Control system for automotive vehicle headlamps and other vehicle equipment

ABSTRACT

A control system is provided for controlling the energization of the headlamps on a first automotive vehicle, the headlamps being electrically energizable and each having a high beam state and a low beam state. The system includes means for collecting light emanating from a second vehicle and means for collecting ambient light. Sensing means is provided which is effective to selectively sense the intensity of the collected light emanating from the second vehicle and the collected ambient light. In addition, the system includes means controlling the state of the beams of the headlamps as a function of the sensed intensity of the beam of light emanating from said second vehicle, and means controlling the electrical energization of the headlamps as a function of the sensed ambient light.

Thisb application is a continuation of application Ser. No. 08/585,863,filed Jan. 16, 1996 now abandoned, which is a continuation ofapplication Ser. No. 08/225,185, filed Apr. 8, 1994 now U.S. Pat. No.5,537,003.

BRIEF SUMMARY OF THE INVENTION

This invention relates to control systems for automotive vehicleequipment, and, more particularly, to an improved control systemparticularly adapted for use in automatically controlling theenergization and the state of automotive vehicle headlamps and othervehicle equipment.

Controls to sense the headlamps of oncoming vehicles and to respond byautomatically dimming the headlamps of the vehicle in which they areinstalled have been commercially available at least since the 1950's.However, such controls have not generally been successful in detectingthe tail lamps of vehicles traveling ahead of the vehicle equipped withthe control. As a result, drivers were still required to manually dimheadlamps for a leading vehicle or else compromise the safety of thevehicle's occupants by subjecting its driver to blinding glare in itsrearview mirrors. Because no one introduced a control to successfullysolve this problem, most of the major automobile manufacturers havewithdrawn their headlamp dimmer controls from the market. Thiswithdrawal from a once profitable market is testimony to the fact thatthe problem is both serious and difficult to solve.

A related headlamp control is one which automatically turns theheadlamps on for driving in dark or dimly lighted conditions and turnsthem off when the daylight is bright enough that the headlamps are notneeded. Typical controls of this type also have deficiencies but operatewell enough to be desirable and are available on many automobiles. Theheadlamp on/off controls traditionally utilize a sensor which viewsgenerally upward to sense the skylight condition. This sensor viewingarrangement has a number of advantages since the skylight level fromoverhead is probably the most direct and most stable indicator of thedaylight condition. The biggest problem is that on clear, blue sky days,most of the light comes directly from the sun and the illumination levelfrom a given area of the sky which does not include direct sunlight maybe lower than the light level viewed from the same portion of the sky onan overcast day even when it may be desirable to have the headlamps onduring the overcast day but not the clear day. In other words, if thethreshold of a present day headlamp on/off control is adjusted to turnthe headlamps on at the desired light level on a blue sky day it tendsto turn the headlamps on at too low a light level on cloudy days. Thus,the headlamps are left off when they are needed on cloudy days therebycreating a hazardous condition. On the other hand, if the control isadjusted to turn the headlamps on at the desired light level on cloudydays, it tends to turn the lights on when they are not needed on clear,blue sky days thereby creating an annoyance to some drivers who do notwant their lights turned on until they are needed. The decision to turnthe headlamps on or off normally comes close to dawn or dusk when thesun is very low in the sky or may even be below the horizon so thatmerely looking at the sun is not a viable alternative.

The two control functions just mentioned are related but distinct andhave been served by separate light sensors in every case known to theinventors. Furthermore, they have normally been served by separateelectronic control modules even in instances where the driver relatedcontrols have been combined. It is desirable to share the same sensorfor both control functions and possibly to extend the use of this sensorto some other functions such as light sensing to estimate heat load fora climate control system or ambient light level sensing for an automaticrearview mirror or ambient light sensing for control of instrument panellighting intensity.

For the headlamp dimmer control function, the most important time tosense the tail lamps of a leading vehicle is when the headlamps beingcontrolled are on high beam and are likely to blind the driver of theleading vehicle with glare in the rearview mirrors. The high beams whichare being controlled illuminate the roadway and objects at the side ofthe road for a long distance ahead of the vehicle so that lightreflected back from these illuminated objects may often either bemistaken for or may drown out weak tail lamps. This is a nearlyinsurmountable problem when the light over the full required field ofview is averaged into a single reading. Designers of prior art controlstook two steps to minimize the effect of the light returned from theheadlamps as well as to minimize unwanted dimming due to stray lightsources. First, they restricted the light sensitive viewing area of thecontrols sensor so that it includes very little more than the area fromwhich lights of other vehicles must be sensed. The viewing area chosenwas approximately 6 degrees high by 18 degrees wide. Secondly, theyadjusted and carefully controlled the elevational angle of the sensor'sfield of view making it as high as practical so that the control stillsensed lights from oncoming vehicles while at the same time it rejectedlight from as much of the brightly lighted patch of roadway just infront of the vehicle as possible. These features are both helpful anddid lead to satisfactory sensing of the headlamps of oncoming vehiclesfor some prior art devices but did not lead to generally satisfactoryperformance for the far more difficult problem of sensing the tail lampsof leading vehicles. To summarize the problem, the high beams project alarge amount of light into the area which must be viewed to detectvehicles for which the headlamps must be dimmed. Each object illuminatedby the headlamps in this area reflects some light back. When thisreflected light is summed over the entire required viewing area, thetotal light level may be quite substantial, easily obscuring what may belittle more than "pin points" of light from tail lamps several hundredfeet away.

Typical prior art headlamp dimmers have utilized easier to applyphoto-resistive sensors instead of photo-diode sensors. The presentlyavailable photo-resistive sensors are not a practical option for themultiplexed sensor of the preferred embodiment of the invention becauseof their slow response speed. The photo-resistive sensors have not beenused exclusively in prior art devices. For example, a headlamp on/offcontrol, manufactured commercially by the assignee of the presentinvention, and described in copending application Ser. No. 07/670,258,filed Mar. 15, 1991, and incorporated herein in its entirety byreference, utilizes a photo-diode. The low current output levels of thephoto-diodes and the drastic increases in leakage current levels atelevated temperatures created serious design problems which were solvedbut the solution increased the electronic circuit cost even for sensingthe relatively high threshold light levels present in such prior artcontrols. The light levels and the resulting photo-sensor currents whichmust be measured by the preferred embodiments of this invention in thecolor sensing functions and the tail light sensing function for theheadlamp dimmer control are a very small fraction of the correspondingoperating light and current levels of the aforementioned prior artdevice. This requires a quantum improvement in the ability to measureextremely low light levels at a modest price.

In a typical light sensing application, it may be impossible todistinguish electrical current due to leakages in the electroniccircuit, particularly in the photo-diode itself from the electricalcurrent due to a sensed light level. Thus, the magnitude of theseleakage currents frequently establish the lowest light level which maybe reliably measured by the photo-diode sensor. The ambient temperaturearound the control when the vehicle is parked in the hot sun can easilyreach 85 degrees C. A rule of thumb is that diode leakage currentsdouble for every 10 degrees C. increase in temperature. This would leadto a 64 to 1 increase in the leakage current of the photo-diode and thusin the minimum light level that could be reliably sensed in going from25 degrees C. to 85 degrees C. The leakage current in many photo-diodesmore than doubles for every 10 degrees C. increase in temperature so the64 to 1 increase is an optimistic estimate and the real world situationis even worse than this. The low light level sensing problem justdiscussed is not unique to photo-diodes and it should be understood thatmany of the features of this invention apply to other light sensors aswell. It should also be understood that the photo-diode is the preferredbut not the only light sensor which may be used in the presentinvention.

A photo-diode or other silicon based sensor and the associatedelectronic circuit which maintains a leakage current which is low enoughto assure proper operation at the extremely low light and hightemperature levels encountered in the application of the preferreddevice would be prohibitively costly. The alternative is to block or atleast partially block the light which shines on the sensor periodicallyand to read the sensor output under this darkened condition. The readingmay be referred to as the zero light level reading even though it mustbe understood that the term zero here is not to be taken in the absolutesense since the concept still works when the light level is sufficientlyreduced by the blocking means. Light to the sensor is blocked and thezero light level reading is taken and then used to correct or at leastpartially correct the actual light level readings for the residualreading errors of the control. It is not easy or inexpensive toperiodically block the light to the sensor and this blocked lightreading must be taken fairly frequently to be effective because of thehigh dependence of many of the causes of the zero reading errors onchanging conditions. As an example note the reference above to thedependence of the sensor leakage current on temperature.

The general light interrupting approach just described has been used invery expensive laboratory equipment such as spectrophotometers tocorrect for residual reading errors and also to compare a measured lightlevel with an input light level in an optical bridge configuration. Thearrangement is sometimes referred to as a light chopper. The inventorsof the present invention are not aware of the application of the lightchopping technique to any modestly priced devices nor are the inventorsaware of any application where the cost of providing the periodic lightblocking for the chopping operation is leveraged by utilizing sharedcomponents of the light blocking structure to perform one or more of thefunctions of spatial scanning, multiplexing of inputs from independentsources, or of multiplexing of color filters for color or color balancesensing functions. All of these functions are incorporated in preferredembodiments of the present invention.

IMPROVED STEPPING MOTOR

In the preferred embodiments of the invention described herein aspecialized reversible motor which provides a dual rotary andtranslating movement is utilized to drive the combined, spatialscanning, light chopping, color and color balance sensing, and lightinput multiplexing functions. It should be noted that except for thefull two dimensional spatial scanning a unidirectional motor or moreconventional bi-directional motor may be used. Such devices which meetsome of the many objectives of this invention are within the scope ofthis invention. Furthermore, many other bi-directional motors can beadapted to drive even the spatial scanning arrangement. The rotor andbearing arrangement in the preferred embodiments resembles that which isused in small brushless DC fans. Except for this resemblance, thedevices are very different since the brushless fan motors are singlephase unidirectional devices designed for relatively high rotationalspeeds. In this description, the word "phase" is used generally toindicate the number of stator poles in the smallest group of stator androtor poles which form a group which may then be radially copied to formthe complete stator and rotor array of poles. This is the geometricconfiguration made without regard to the polarity of the poles. A normaltwo phase motor has two stator poles for a single rotor pole and thispattern repeats. A five phase motor has five stator poles for four rotorpoles which makes up the entire pole configuration or repeats. The word"phase" is used herein to indicate the magnetic configuration and notthe number of controlling inputs connected to the motor.

The specialized requirements for the motor have been satisfied by usinga number of innovative features. The axial translating feature of thepreferred embodiments is not related to the features described here andit should be understood that the motor of the preferred embodiments canreadily be used without the translating feature and should be applicableand advantageous in a large number of stepping motor applications wherejudicious cost and performance trades can be made beneficially. Themotor in the preferred embodiments utilizes a single winding on each ofthe five poles of the motor stator and the five stator pole facewindings are all connected in series to a power supply source. Controlof the motor stepping is accomplished by providing transistors toselectively short the windings which encircle each of the individualstator pole faces. Two (preferred) or three of the five individual poleface windings are shorted at any one time so that three (preferred) ortwo of the poles, respectively, are energized. The main distinguishingfeatures of this motor from the known prior art is that it is a steppingmotor capable of bidirectional operation utilizing a permanent magnetrotor and for the normal operation of which each electromagnetic statorpole is energized to only one predetermined magnetic polarity by theenergization of any winding or windings which encircle it. Any reversalin the magnetic polarity of the pole from its actively driven polarityis due to the combined effects of the permanent magnets in the rotor andto the energization of windings which encircle other poles in the motor.An optional additional feature of the motor is that the individual poleface windings are connected in series to form one continuous windingwhich is energized by connection of the entire series winding to a powersource with stepping action controlled by providing and exercising meansto selectively short windings about the individual pole faces. Shortingof an individual pole face winding has the effect of diverting theseries current around the winding thereby removing the source ofenergization of the pole face to the predetermined polarity. A furtheroptional feature is to step the motor using a sequence for which amajority of the pole face windings are energized to their predeterminedpolarity in all of the static stepping states. A further optionalfeature is to use a two pole permanent magnet rotor with a three polestator and to apply the rules of construction above. A further optionalfeature is to use any given even number of poles which is greater thanone for the rotor and to provide the given even number plus one statorpoles and then to generally extend the rules and stepping patterns givenfor the five pole motor to the resulting motor. A further optionalfeature is to increase the number of stator and rotor poles by anintegral factor n by adjusting the angular arrangement of the baseconfiguration so that it fits in one nth of a revolution and thenfilling out the configuration by making a total of n radial copies ofthe configuration. The n corresponding poles are directly connected inseries or in parallel and the series or parallel combinations areconfigured in the same manner as the individual poles of a version nothaving the duplicated groups of poles. A further optional feature is tocontrol the motor from a micro controller programmed to energize andstep the windings in accordance with the required patterns. With themicro controller, many options and variations are available in thecontrol sequence. For example the motor might be controlled for smootherstepping or greater positional accuracy by momentarily providing stepsfor which fewer than a majority of the windings are energized and somerule might be followed to cause the motor to energize a majority of thewindings for step periods of longer duration. Of course, one is notrestricted to the stepping mode where the majority of the poles areactively driven. This is an option which is highly beneficial for someapplications. A further option of the design is to use a cogged typecompound construction on the rotor and stator to increase the effectivenumber of poles for applications requiring finer stepping resolution,such implementation being by means similar to that used for prior artpermanent magnet rotor two phase and five phase designs.

Motors known to the inventors which are also five phase but which areotherwise quite different are motors from Berger-Lahr GmbH, BreslauerStrasse 7, D-77933 Lahr, West Germany and from Oriental Motor USA Corp.,2701 Plaza Del Amo, Suite 702-A, Torrance, Calif. 90503. All of thesefive phase motors known to the inventors drive each pole actively toeach of its two different magnetic polarities by reversing the currentin the winding which encircles it. These motors are driven either fourphases at a time, five phases at a time or in a combination of four andfive phases at a time instead of two or three phases at a time which areenergized in the preferred embodiments of the present invention. Knownprior art motors also use a duplicated pole configuration so that aminimum of ten stator poles rather than five are provided. Furthermore,these prior art motors require a complex drive which has bipolar drivecapability to each of the five motor leads and which with driveelectronics cost hundreds of U.S. dollars each in small quantities.Production versions of the same drivers could be much less expensive butthere is almost no chance of meeting electronic parts cost goals in therange of one dollar for this type of electronic drive without drasticdesign changes.

A popular practice with other types of stepping motors, such as twophase motors, is to provide two opposing windings which encircle thesame pole and to always energize one of the windings to drive the poleto one magnetic polarity and to energize the other winding to drive thepole to its opposite magnetic polarity.

A number of features are needed to provide a low cost stepping motor. Tobe powerful and reasonably efficient for its size, any small motor needsto utilize a permanent magnet to maintain a strong magnetic field withwhich the electromagnets in the motor can interact. To have ten or moresteps per revolution without going to a more expensive compound design,a permanent magnet having four or more poles is desirable. The greaternumber of poles on the permanent magnet also reduce the stray magneticfield and the magnetic shielding required to make it possible to use amagnetic compass close to the motor. It is very important to use adesign which requires a smaller number of turns of magnet wire, areasonably small number of separate windings, and which uses a magnetwire size that is large enough to be easy to wind and to terminatereliably without danger of breakage or corrosion damage. For economy itis desirable for a stepping motor for which stepping rate requirementsare modest to have its winding(s) energized directly form the DC voltagesupply (12 volts in the typical automobile). Use of the permanent magnethas one very large disadvantage. Practically any configuration whichuses them requires reversal of the magnetic polarity of the electricallyenergized poles of the motor. This has normally been accomplished byproviding transistor switches to reverse the polarity of at least twowindings in a DC stepping motor or by the provision of a duplicatedreversed winding on each of the motors electromagnetic poles. In eithercase poles are actively driven to their north pole polarity during somepart of the stepping sequence and to their south pole polarity duringsome other part of the stepping sequence. Typical two phase steppingmotors are either driven with two composite windings which areindependently reversible or by four composite windings which can bedriven with unipolar drives. This latter design has two windings perpole as described above which are configured as composite windings towork with the four input unipolar drive. A conventional two phasestepping motor requires windings for twice as many pole faces as thereare poles on the electromagnet in the rotor. This requires eight poles,each needing a winding, in order to use the desirable four polepermanent magnet rotor. As an "economy" measure to enable the motor tobe driven by four single transistor switches instead of the two morecomplex bipolar transistor drive circuits, the motors are frequentlyprovided with two windings of opposing direction on each pole asmentioned above. This requires sixteen instead of eight windings for thefour pole, two phase motor resulting in many more turns of much finerwire for a given application. The typical five phase motor oftenarranges the five windings in a pentagon configuration for which each ofthe five "corners" or connections between windings must be driven with areversible, bipolar drive. Furthermore the windings in a lower costconstant voltage five phase drive are frequently run with four of thefive windings simultaneously operated at voltages nearly equal to thesupply voltage. Thus where a supply voltage of more than two or threevolts is used, each winding must have numerous turns of fine wire forthe constant voltage drive. For an automotive application, it isdesirable to use 12 volts so there must be enough turns of fine enoughcopper wire to provide enough resistance to limit the current. If, forexample the motor winding power dissipation is limited to 1.44 watts at12 volts, the total current for the four windings is 120 milliamperes sothe current for each winding is 30 milliamperes. This requires 400 ohmsper winding or 2000 ohms total for the five windings. It would, forexample, require 930 feet of very fine 43 gage wire to equal thisresistance and even greater lengths of wire of larger, more reasonablesize.

There are some surprisingly effective economizing compromises which areincorporated in the five pole motor used in the preferred embodiments ofthis invention. First, five stator poles can be used instead of theusual ten for the magnetically symmetrical prior art five phase motors.Second, with the five pole design, the predominance of successive poleswith alternate polarity in the magnetic configurations used to step themotor makes it practical to drive only poles which need to be of onepreselected polarity in a particular motor step position and de-energizewindings around the remaining poles thereby allowing them to bepassively forced to their operating magnetic state. The general runningconfiguration for a five pole motor is to have four of the poles ofalternating magnetic polarity. Thus, if the option to drive three polesat a time is used, each non driven pole has neighboring poles on eachside which are driven to the other polarity. This arrangement enhancesthe ability to passively drive the non energized poles to their desiredpolarity. The object of the arrangement is to avoid the great amount ofextra electronics or the duplicated windings with many turns of finewire required to provide the active magnetic reversal for the poles. Thetechnique may also be extended to two phase motors, but passive magneticdrive of the non driven poles will not be as successful because themotors are normally operated with two adjacent poles of one polarityalternated with two adjacent poles of the opposite polarity instead ofwith the pattern for the preferred motors which alternates polarity forevery adjacent pair of poles but one.

There are several options for the winding drive configuration. The firstconfiguration is a parallel one in which each of the five windings hasone end connected to the supply and the other to a transistor switch toground. The winding polarity is such that each pole is driven to itspredetermined polarity when its transistor switch is turned on. Thetransistor switch is turned off to de-energize the winding allowing theactive poles to passively force it to the opposite polarity. Then onlywindings on the poles which need to be driven to the preselectedpolarity in the stepping sequence are energized and the windings on theremaining poles are de-energized. As a second option, the windings areconstructed with fewer turns of heavier wire and connected in serieswith the winding directions arranged so that when the end connections ofthe series windings are connected to a DC power source, all of the polesare energized to the same predetermined magnetic polarity. Thus,windings from more than two different phases of a stepping motor areenergized in series. The preferred embodiments energize all of thewindings in series. A transistor configuration is then added withnecessary protection circuitry which permits selective shorting of theindividual pole winding sections. The stepping sequence is thenaccomplished by supplying a continuous DC voltage or current to theseries winding and selectively shorting the individual pole windingsections which correspond to the individual poles which should not beenergized to the predetermined polarity. Each shorting transistor servesto selectively shunt the current around the winding encircling aparticular pole so that the pole is not forced to the predeterminedpolarity.

As an illustration, assume that the motor is stepped in a mode wherethree of the five windings are always energized, and assume that themotor is of a size which will dissipate the heat from 120 milliamperesof total current. This is 40 milliamperes per energized windingrequiring a winding resistance of 300 ohms per winding for a twelve voltsupply. The total resistance of the five windings is 1500 ohms. Thus theparallel winding configuration with the unipolar energization doesreduce switching complexity very substantially over a full bipolar driveof the prior art five phase stepping motor but winding resistance isstill too high for small motors run from higher voltage sources. Nowconsider the same motor driven with all its windings energized in aseries configuration across the power supply. The nominal powerdissipation should be the same so the current through the series windingshould be 120 milliamperes. To keep the ampere turns the same for eachpole, the number of turns in each winding should be one third of thenumber used for the parallel configuration because the series windingcarries three times the current. To establish 120 milliamperes, thetotal resistance for the three non shorted windings should be 100 ohms.and the resistance of the individual windings should be 33.3 ohms. Thetotal resistance of the five series windings is 166 ohms. In going fromthe parallel to the series configuration, the total resistance of eachwinding section has been reduced by a factor of 9. To do this the wirelength is decreased by a factor of three as are the number of turnswhich must be wound and the wire cross-sectional area is increased by afactor of three. The wire in the series winding takes three times theamount of force to break it and its diameter is 1.73 times the diameterof the wire in the parallel winding. Furthermore the series winding iswound as one continuous piece of magnet wire with the wire simplywrapped around a terminal before and after the winding of each pole facesection. The five pole face windings for the parallel version must bewound as separate windings with the corresponding end of each attachedto a common terminal and the opposite end of each to an individualterminal. In a typical application four additional transistors and fourto eight additional resistors are needed to drive the series arrangementand a higher current carrying capacity is required for the shortingtransistors. This is a small price to pay for the greatly reducedwinding problems.

The arrangement just described is also applicable for a two polepermanent magnet rotor driven by a stator having three wound poles orfor a six pole permanent magnet rotor driven by a stator having sevenwound poles or in general for any arrangement having an even number ofat least two poles for the permanent magnet rotor and the next higherodd number of wound poles for the stator.

An object of the present invention is to overcome disadvantages in priorautomobile headlamp dimming and on/off controls of the indicatedcharacter and to provide an improved headlamp dimmer control which maybe installed on a vehicle and which incorporates improved means forsensing the tail lamps of a leading vehicle when the leading vehicle isstill far enough away for the controlled headlamps of the trailingvehicle to be dimmed to prevent causing excessive glare for the driverof the leading vehicle.

A further object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means to detect the redcolor of the tail lamps of a leading vehicle to aid in thediscrimination of the tail lamps from other light sources.

A further object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for limiting theinstantaneous field of view of the headlamp sensing sensor to a smallerportion of the total field of view so as to minimize the obscuringeffect of the total light emanating from other sources, especially fromthe road and other objects illuminated by the headlamps which are beingcontrolled.

A further object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for scanning thefield of view so that the required total viewing area is covered by asensor which has the smaller instantaneous field of view.

A further object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for taking a sensorreading when the light level from the sources to be measured issubstantially blocked so that the circuit response due to leakagecurrents, to other circuit effects, and possibly to stray or residuallight levels reaching the sensor can be taken into account and at leastpartially nullified.

A further object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for utilizing thelight sensor reading with the blocked light sources to decrease thelowest light level which may be reliably sensed by a factor of three toone and preferably by a much larger factor.

A further object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for utilizing thesame sensor to measure more than one component color.

A further object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for utilizing thesame sensor to separately measure the light from more than one areawithin the total field of view of the headlamp dimming sensor.

A further object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for utilizing asensor with a single sensing area and which does not require separateamplifiers or electrical multiplexing of low level signals to accomplishtwo or more measurement functions.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for using only onesensor with only one sensing area and one amplifier means to perform thedesired sensing functions.

A further object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for measuring thebalance between a color component which is weighted toward the shortwavelength part of the color spectrum relative to another colorcomponent which is not similarly weighted in order to at least partiallydifferentiate between a cloudy and a blue sky day.

A further object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for using the samesensor to perform part of both the headlamp dimmer and the headlampon/off sensing functions.

A further object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for sharing acommon color discriminating means for both headlamp dimmer and theheadlamp on/off control functions.

A further object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for using a singlephoto-sensor with a single electrical output and amplifying means forcombined headlamp dimmer and headlamp on/off sensing functions.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for including lightreadings for fields of view which differ substantially from one anotherin both horizontal and vertical directions.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for including lightreadings for fields of view which are close in horizontal direction butwhich differ substantially in vertical directions.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for including lightreadings for fields of view which are close in vertical direction butwhich differ substantially in horizontal directions.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for including lightreadings from fields of view which have substantial overlap, one toanother.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for arranging therelative placement of multiple samples of light levels so that togetherthey include the entire area over which high beams from the vehiclewhose lights are under control are likely to cause glare for the driverof another vehicle in order to detect the lights of the vehicle and torespond by dimming the headlamps.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for using a motorto facilitate a scanning function, and/or a multiplexing function and/ora color component selection function and/or a light blocking function.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for using amechanical assembly which performs a substantial portion of its functionwith one moving assembly.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for using a motorwhich limits both the magnitude and the variability of its straymagnetic field well enough to be used in close proximity to a sensor fora magnetic direction finding compass and so that it may meetrestrictions placed on magnetic field levels to which vehicle occupantsmay be subjected.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for synchronizingor otherwise correlating a compass reading function with the operationof a motor so that the effect of the magnetic field may be minimizedand/or compensated for.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for providing amotor having a reduced number of turns of heavier wire to facilitatewinding and to minimize failures due to wire breakage or corrosion.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for providing amotor which requires only one winding per pole to facilitateconstruction.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for providing amotor which requires each of its magnetic poles to be driven to only onemagnetic polarity by the winding which encircles it.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for providing abi-directional motor which utilizes one continuously energized tappedwinding connected in a series configuration across a power supplywhereby stepping and direction control is accomplished by selectivelyshorting or partially shorting segments of the winding between taps.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for using areversible motor whose rotor moves in both a rotary and a translationaldirection in order to accomplish the desired functions.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for using a motorfor which windings on a majority of but not all of the poles aresubstantially energized while the remaining poles are substantiallyde-energized and thereby force the magnetic state in each of theremaining de-energized poles to a predetermined magnetic polarity.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for forcing all ofthe substantially energized poles of a motor to the same magneticpolarity and to thereby force the remaining substantially de-energizedpoles to the opposite polarity.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for utilizing abi-directional stepping motor with an odd number of wound physicalpoles.

Another object of the present invention is to provide an improvedheadlamp dimmer incorporating a moving baffle to minimize interferenceof one optical signal with another.

Another object of the present invention is to provide an improvedheadlamp dimmer incorporating colored mirror reflectors to separatecolor components in input signals.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for arranging amotor and screw and a rotary selector so that they fit together in acompact structure.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for arranging themechanical parts thereof so that high reliability and reproducibilitycan be achieved without having to maintain unrealistically tighttolerances.

Another object of the present invention is to provide an improvedheadlamp dimmer incorporating a positive, non-binding stop at at leastone and preferably both ends of the travel range whereby one of thesestops serves to establish a home position for the unit and together thestops serve to assure that the unit cannot be driven to a position inwhich it could jam.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for incorporatingthe filters with a reflector as a light transmissive body of a secondsurface mirror so that the filtering and reflection are achieved withonly one exposed optical surface.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for incorporatingfilters separately on a moving member in a headlamp control to eliminatethe sensing of unfiltered first surface components in a mirror.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for utilizing anegative focal length entrance lens of larger cross-sectional area thana light pipe or light directing means to which it attaches in order toincrease the amount of light which is sampled over a wide viewing angleand which is directed into the light pipe.

Another object of the present invention is to provide an optical sensorwhich has a light concentrating lens which in operation does notmaintain focus on a sensor or other vulnerable spot for a sustainedperiod of time thus taking the risk that the sun's rays will be focusedon the spot for a long enough period of time for heat to build and causedamage.

Another object is to provide a unit which positions a reflector in aposition which does not permit the sun's rays to come to focus and causedamage while the unit is inactive.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for utilizing anarray type light sensor.

Another object of the present invention is to provide appropriatedimensional offsets so that corresponding fields of view taken withvarious color filters register closely with each other.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for causing theheadlamp dimmer portion of the control to respond to an increase inreading due to a sensed scattered light level from suddenly visiblebright oncoming headlamps in a way which causes the control to decreasethe delay in dimming the controlled headlamps.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for providing morethan one sensing port and associated optics with each port beingrotatable to bring it into alignment with an optical signal source.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for providing morethan one optical signal source to which at least one associated sensingport may be rotated to achieve optical alignment to take a reading.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for simultaneouslyproviding more than one sensing port each of which is focused on acommon sensor during a portion of its rotary motion and which duringsaid portion of its rotary motion is brought into alignment with morethan one optical source at different parts of said portion of its rotarymotion.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for providing morethan one sensing port each with a different sensing feature such as adifferent filter or sensing port aperture or lens configuration as partof a rotary assembly.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for coupling asensor efficiently to an optical signal transmitted by a light pipe.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for providing forthe selection of at least three and up to six or more differentselectable filters in a selected combination which can be usedsequentially in any desired sequence to read inputs from a selectednumber of the optical signal sources.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for using aseparate lens which is not part of a rotating assembly to approximatelyfocus an image on the a surface into which a sampling port or ports maybe positioned whereby the optics and filters associated with thesampling port then filter and redirect or re-focus at least a portion ofthe image which impinges on the port directing it to a photo detector.

Another object of present invention is to provide an improved headlampdimmer control incorporating improved means for using rotary motion of ahead to change position of a sampling port within the image field ofseparate lens to obtain sensor readings for different areas of theseparate lens's projected image.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for making anadjustment, such as translation of a rotary head along its axis ofrotation, or movement of a sensor or lens to accomplish sampling of thefield of view in a portion not covered by a simple rotary sweep of anaperture through a field of view.

Another object of the present invention is to provide an improvedheadlamp dimmer control incorporating improved means for using lightgathering means for each signal input which gathers the proper amount oflight to place using a signal to be measured within the measuring rangeof a common sensor.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a simplified pictorial diagram viewed through the windshieldwhich depicts the application of a combined headlamp dimmer and headlampon/off electro-optical sensor unit embodying the present invention.

FIG. 1a is a simplified block diagram which includes blocks depictingmajor components of the device of this invention and several blocks withwhich these components interface.

FIG. 2 is an exploded view which depicts the mechanical, optical, andelectro-optical components in the combined headlamp dimmer and headlampon/off control embodying the present invention.

FIG. 3 is a view of the optical structure and rotary sensing headpositioned to sense light for the headlamp dimmer function.

FIG. 4 is a view of the optical structure and rotary sensing headpositioned to sense light for the headlamp on/off function.

FIG. 5 is a view of the optical structure and rotary sensing headpositioned to take a reading when most of the light to the sensor isblocked.

FIG. 6 is an exploded view of the motor bearing and stator assembly.

FIG. 7 is a schematic block diagram of the electrical control circuitwhich details the stepping motor winding and drive configuration.

FIG. 7a is an optional shorting circuit for one of the series pole facewindings.

FIG. 8 is a list of stepping motor shorted winding control inputs and ofthe resulting polarities to which the magnetic poles are driven by nonshorted encircling windings.

FIG. 9 is a subset of entries from FIG. 8 for which three (a majorityof) the pole face windings are energized.

FIG. 10 is a simplified diagram of an alternate embodiment of theelectro-optical sensing module which is suited to color measuringapplications and which is depicted in a position to sense a light levelfocused by an external lens.

FIG. 10a is a top view of the configuration depicted in FIG. 10.

FIG. 11 is a perspective view of the device of FIG. 10 depicted in aposition to sense a light level transmitted to the unit by a light pipe.

FIG. 11a is a top view of the configuration depicted in FIG. 1.

DETAILED DESCRIPTION Electro-Optical Sensing Module Description

Referring to the drawings, the simplified pictorial diagram in FIG. 1depicts the application of the electro-optical sensing structure for thecombined headlamp dimmer and headlamp on/off control which embodies thepresent invention and which is shown in an exploded view in FIG. 2. Inthe block diagram of FIG. 1a, the light sensor 1, the combined sourceselection, scanning, and color detection device 151, the light blockingmeans 150, the light collecting means for the ambient light function 3a,and the light collecting means for the headlamp dimmer function 2a arenormally housed in the module 100 of FIG. 1. Portions of the remainingcontroller and user and vehicle interface functions depicted in blocks153, 154, and 155 may be included in module 100 and other portions maybe placed elsewhere.

The multiple functions of block 151 are primarily performed by theassembly shown in FIG. 2. FIG. 2 also depicts components for theindividual light collecting means 2a and 3a, the light blocking means ofblock 150, and of the light sensor 1. Details of portions of theassembly of FIG. 2 and of configurations for particular operating statesthereof are depicted in FIGS. 3 through 6.

The controller 153 controls the source selection, scanning and colordetection functions of block 151 via control of the stepping motorcontained in block 151. Unique features of the motor and details of thecontrol function are detailed in various sections throughout thisdisclosure and details of the motor control and stepping sequence aredepicted in FIGS. 7, 7a, 8, and 9 and the associated description.

Although many features of this invention apply for separate headlampon/off and headlamp dimmer control functions, the embodiment shownperforms both functions, thereby benefiting from utilizing sharedresources. Although there is great benefit from sharing many of theresources for the two control functions, it is necessary to provide somefeatures which are individually adapted for their specific function. Themost notable of these special individualized features are the headlampon/off control light collecting means 3a and the headlamp dimmer lightcollecting means 2a. As will be explained later, the light collectingmeans 3a for the headlamp on/off control function covers a broad viewingarea and in the embodiment shown, this field of view is not scanned. Thelight collecting means 2a for the headlamp dimmer function, on the otherhand, covers a relatively restricted total field of view and thescanning function serves to further break this field of view intoconsiderably smaller sub fields as will be described in detail later.Light from each of the fields of view for the two functions is directedto a unit which serves to select and thereby multiplex the two inputs aswell as to perform scanning, color distinction, and reading errorcorrection functions which are of benefit to one or to both of thesensing and control functions. Note that the viewing direction, therequired field of view and the choice to scan the field or to not scanthe field are all very different for the two sensing functions. It ismost practical to provide individualized light collecting means forthese two functions and to provide a selection means to access themindividually as opposed to attempting to use a single shared lightcollecting means with a wide angle field of view to perform bothfunctions. A sensing light collecting means having a single field ofview and having both the sensitivity and the resolution to serve theheadlamp dimmer function and the extended field of view to serve theheadlamp on/off function would be unnecessarily elaborate and expensive.The use of individualized light collecting means followed by theselection means is an important feature of the invention which may beused with other sensors and with other means of optical selection.

It should be apparent that features of the device for optical sourceselection may be readily extended to perform many other opticalfunctions as to, for example, perform the ambient light sensing functionfor an automatic rearview mirror.

The view in FIG. 1 is through a vehicle windshield 102. The mechanism ofFIG. 2 is housed with associated electronics in a case 100 which ismounted to a button 101 on the windshield 102 of the vehicle along witha rearview mirror 103. Driver controls for the unit may be incorporatedon the mirror housing and associated electronics for the low levelelectrical signals from the light sensor should be included in the case100 but the remaining electronics may optionally be placed elsewhere ordispersed to any desired locations. With the embodiment shown, it isassumed that some of this electronics is in the mirror housing. Thecable 104 supplies power and connects control input and output signalsto the headlamp control case 100 and connects these signals to themirror 103. The cable 105 in turn connects the mirror 103 to thevehicle's power supply which includes both the conventional continuouslyenergized vehicle 12 volt supply and the conventional ignition switched12 volt supply. The cable 105 also connects to a relay or relays whichenergize and de-energize the headlamps, running lamps, and tail lampsand to a relay which switches between the vehicles high beam and lowbeam configurations. Outputs and/or two way communication related to theabove and also to other features such as an ambient light sensor for usein the control of a rearview mirror, in an instrument panel intensitycontrol, or in a vehicle heat load control may also be provided. Otherlight inputs may be routed to the sensor module and their readingsmultiplexed with other readings in some embodiments of this invention.The relay functions may be accomplished by either electronic orelectromechanical means. The light guide and entrance lens assembly 3for the headlamp on/off function extends forward from the case 100 sothat light from a wide area of the sky falls on its entrance lensthrough the windshield 102 and a portion of this light is directed toand sampled by the sensing unit in case 100. Likewise the lens 2 may bepositioned with reasonable but not extraordinary precision to view theheadlamps of oncoming vehicles and the tail lamps of leading vehiclesand to communicate and focus these signals on the unit's sensor. Thesensor units both view through a portion of the vehicle windshield whichis kept clear by the vehicle's windshield wipers.

FIG. 2 is a simplified diagram of the headlamp control and ambient lightsensing electromechanical assembly which is mounted in the case 100. Thelight guide and integral lens and reflector 3 and the lens 2 areattached to and view through an opening or window in the case 100. Thesensor 1 is secured and electrically connected in a stationary positionon a circuit board (not shown) in the case 100. Components 4, 5, 6, 7and 8, which will be described hereinafter in greater detail, areattached together in a rigid assembly which rotates and translatesaxially as will be described herein. Components 9 through 15, which willalso be described hereinafter in greater detail, form the stator,bearing, and stop assemblies for the motor. The motor winding coil formsare depicted but the windings are not. The stator, bearing, and stopassembly is secured and electrically connected in a stationary positionto a second circuit board (not shown) in the case 100. The circuitboards to which the sensor and motor assemblies are attached alsopreferably have a portion of the headlamp control circuit on them andare interconnected to each other and to the cable 104.

The components 4 through 15 form a motor which rotates and translatesthe rotary head 4 to perform a combined optical signal selection,optical signal blocking, optical signal scanning, and color filterselection process which will be described hereinafter in greater detail.The components 1 through 4 are shown in their normal operatingpositional relationship and the remaining components are shown inexploded view to facilitate description of their form and function.

Detailed Motor Description

The component 5 is a cylindrical metal can of light weight havingcylindrical sides and a generally conical top which nests with theinclined mirror surfaces 4a and 4b of the rotary head 4. The can 5slides into the bottom of rotary head 4 and is secured therein in arelationship which maintains close axial alignment of the parts. Thehole 5d registers with an internal, axially aligned, cylindricalprotrusion (not visible), which extends axially downward from theintersection of mirrored surfaces 4a and 4b in the interior of therotary head 4. Close registration of the hole 5d with the protrusionmaintains the axial alignment between the rotary head 4 and the can 5 atthe top and a close fit preferably augmented with radially spaced veryshallow internal ribs on the inner surfaces of the cylindrical portionof the rotary head 4 maintain the axial alignment at the lowerextremities of the rotary head 4 and the can 5. The parts are fastenedtogether to form a secure unit. The can 5 is preferably made of a highpermeability, low magnetic hysteresis magnetic material (optionally of ahydrogen annealed nickel iron material such as might be used in themagnetic structure of the thermocouple safety on a gas appliance) inorder to contain the magnetic field from a magnet 8 and minimizeinteraction with the sensor for a magnetic compass in applications wheresuch a sensor is mounted within several inches of the motor.

The open cylindrical structure 8 is a ferrite ring magnet having fourequally spaced N-S-N-S poles on its inner cylindrical surface. It ispressed into the cylindrical portion of member 5 so that its shape andposition are maintained by the can 5. The height of the magnet 8 is madegreat enough to provide an adequate magnetic field for the stator as ittranslates through its entire translational range of about fivemillimeters. The design is preferably but not necessarily made with thefour pole permanent magnet structure rather than a two pole structure tohelp minimize the radiated magnetic field. When assembled the rotaryhead 4, the can 5, and the magnet 8 form a rigid assembly with theirlower edges approximately aligned. If the number of poles are changed,the stator and its related circuit must be altered to match.

Portion 7a of shaft 7 is pressed into an axially aligned hole in theinternal cylindrical protrusion (referred to above) in the rotary head4. The shaft becomes a rigid part of the assembly and is held in preciseaxial alignment by the press fit into a hole which engages the shaftover a length which is great enough to provide precise axial alignment.The member 6 is a screw thread which is pressed onto shaft 7 or as adesirable alternate is integrally molded as a portion of the rotary head4. This thread is nominally a 4 millimeter diameter, 1 millimeter pitch,ACME thread which is specially modified to have a generous radialclearance to eliminate the chance of binding. This modification consistsmostly of modestly under sizing the radial dimensions of the screwand/or over sizing the corresponding dimensions in the nut. Preciseaxial centering with the shaft must be maintained. As will be explainedfurther when the stop mechanism is discussed, the threaded part 6 mustalso be positioned so that the axial position versus the angular travelis properly phased with the rotation of the rotary head 4. This is anadditional reason to integrally mold the thread in the rotary head 4.The rotor assembly rotates on shaft 7 and is translated by theengagement of thread 6 with a stationary nut . The unit moves as asingle rigid assembly so that other belts, gear, pulleys, pivots, leversor flexible couplings are not required.

The stator and bearing assembly are depicted by the components 9 through15 shown both in FIG. 2 and from a different perspective in FIG. 6. Thecomponent 10 is a stack of stamped laminations which provide five polesof modest but reasonable width and which are designed to provide maximalaccess for easy winding consistent with their size and magneticperformance. The lamination stack 10 is placed on molded plastic part 11so the cylindrical portion 11a of part 11 extends through circular hole10a in the lamination stack. Plastic part 9a is placed on top oflaminations 10 so that 11a also extends through hole 9a. Together parts9 and 11 nest with the laminations 10 so that they form the top andbottom portions of insulating bobbin type winding coil forms for each ofthe five poles of lamination stack 10. Projection 11d, visible in FIG.2, keys with opening 9b in part 9, visible in FIG. 6. Together with thelaminations, this combination serves to key the nested assembly togetherso that, if rattling is not a problem, the windings should serve tosecure the unit together. Bonding of lamination stack 10 to form a solidunit, alternative construction using a single piece for 10, or theaddition of other mechanical fastening means to hold the stator assemblytogether are all reasonable options. The six pins shown at 12 arepressed into the holes 12a of the part 11 and pin 13 is pressed intohole 13a of part 11. The winding is then added. As shown in FIG. 7, thewinding is made as one continuous winding having sections M1 through M5which are placed in series. Each of these windings sections M1 throughM5 are wound in the same direction around corresponding poles P1 throughP5. The two ends of the winding and the four intermediate taps betweenadjacent pole face windings are connected one each to the six pinslabeled as part 12. Thus the winding can be applied as one unbrokenpiece of magnet wire which is wrapped around respective pins at thestart and end of winding and also between the winding of each pole.

The mating nut 6a for the screw 6 is integrally formed in the top ofplastic part 11. Because of the need for precise axial alignment of thenut and shaft, it is preferable to integrally form this thread in part11. This does, however, require that the material in part 11 serve as alow friction, good wearing part in addition to its other mechanicalrequirements. The nut may alternatively be of a separate piece ofmaterial. Furthermore, the nut may be flexibly constrained especiallyallowing some radial compliance so that it self centers with the thread.These are reasonable options but a plastic which meets the combinedmechanical requirements and a design using a single part will yield themost reliable and cost effective part. Acetal which does not have anabrasive fill is the best material known to the inventors. A Teflon®fill in the acetal plastic may be used to decrease friction. The nut aswell as the thread should be carefully modified to permit adequateradial clearances. Since a rotational speed of several revolutions persecond is normally adequate, the wear problems are not nearly as severeas for rapidly moving parts.

The bearings 14 and 15 are inserted and spaced in the cylindricalopening 15a below the threaded portion at 6a. Shaft 7 revolves andtranslates in these bearings and they guide screw 6 in nut 6a whichcauses the translational motion. Bearings 14 and 15 are spaced as farapart as possible consistent with constraints that they must remainhoused in the part; that the bearing 14 must allow axial clearance forscrew 6 when it is in its lowest position; and that the shaft 7 must notslide out of bearing 15 when it is in its highest position. The view issimplified. Shoulders, spacing sleeves, and/or retainers may be added asneeded to retain the bearings in proper position. The internal screwthread at 6a and the inner cylindrical portion 15a which holds thebearings are preferably molded over a common mold insert so that axialalignment can be precisely maintained. A press fit would be the easiestway to retain the bearings but because of conflicts between fillmaterials which would enhance the dimensional stability of the plasticand the wearing and frictional properties of the molded in nut, it ispreferable to mechanically retain the bearings 14 and 15.

In use the rotor assembly, components 4 through 8, is stepped in knownincrements under the control of the micro controller so that once itsposition is known, it becomes a simple matter of maintaining an up/downcount in the micro controller program to keep track of the rotorposition. It is desirable to initially establish the rotor home positionwhen the controller is turned on and initialized and it is expedient tooccasionally re-establish the home position to correct for any possibleerrors in the stepping positional response. The easiest and least costlymethod to establish the home position is to run the rotor for enoughsteps in one direction that it is certain to have reached the end stopand to have been stalled and held in position by the end stop for theremaining steps. The controller then reverses the direction to move therotor away from the end stop and keeps track of its position bymaintaining an up/down count of the number of steps that the rotor isfrom the end stop used to establish the home position. Besides the needto establish the initial home position, the end stop or stops serve thepurpose to keep the rotor from being driven to an inoperable position inthe event of a temporary program error condition which might cause theunit to be driven beyond its normal positional range. If the rotor isnot driven to an inoperable position, it is likely that the unit candetect that responses are not appropriate (for example, unusually highor variable blocked light sensor readings) and force an initializationand re-homing sequence before serious damage is done. Without the endstops, the unit would be likely to jam, and repair would be required tofree the jam. It is critically important that the stops be reliable andnon-jamming. The tab 4d on the rotary head 4 and the tabs 4e and 4fextending from the arm projecting from part 11 serve this purpose. Theunit is designed to revolve 5 turns thereby translating 1 millimeter perturn for a total of 5 millimeters of travel between stops. For clockwiserotation viewed from the top, tab 4d rotates and travels incrementallydownward 1 millimeter at a time with each completed revolution until ithits stop 4e from the side not axially. This is an important featurethat the stops are designed to first stop the rotary movement which as asecondary result stops the axial translation as well. If the motion wasblocked in the axial direction instead, the screw would tighten and belikely to bind. Also, the rotational position would be indefinitedepending on the tolerances of the screw threads verses the stop and onthe degree of tightening. For counterclockwise rotation tab 4d travelsupward in a helical path until it strikes tab 4f. Implementation of therotary stops is where care must be used in the positioning of the screwand in the relative spacing and in the accuracy and stability of thepositioning of the stop tabs. The dimensioning is controlled so that onthe downward path tab 4d adequately clears (this can be a nominalclearance of 0.4 millimeters.) tab 4e on the last revolution beforeengaging the stop but then squarely engages it (this can be a nominaloverlap of 0.6 millimeter.) on its final revolution as tab 4d engagestab 4e. With the correct spacing between tab 4e and tab 4f relative tothe screw thread pitch and the height of tab 4d, a similar requirementis met as the screw rotates to its counterclockwise extreme and tab 4dengages stop tab 4f. In order to stabilize the position of the tabs, thearm which holds tabs 4e and 4f is attached to part 11 and it is alsoattached to the printed circuit board by post 13.

To assemble the rotor assembly to the stator assembly, the lower end ofshaft 7 is inserted through thread end 6a of the stator assembly andslid into the bearings 14 and 15. Then the threaded portion 6 is screwedinto the nut 6a. Before attachment to the printed circuit board, thestop 4f is easily sprung out of the way to screw the rotor unit into itsproper position with moving stop 4d between stationary stops 4e and 4f.

The circuit board (not shown) has 7 holes and solder pads and alsoprovides the needed electrical connections to these pads. The board alsocontains a cutout to clear the arm 4g and the shaft 7 which may extendslightly through the circuit board when the rotor is at the lower stopposition. The unit is inserted into the printed circuit board until thefour legs 11f and the bottom 11g of the stop leg are firmly seatedagainst the printed circuit board and the legs are soldered in place.Optionally, if the proper stop clearance cannot be controlleddimensionally, the surface 11g can be designed to ride slightly abovethe surface of the printed board and the arm can be adjusted for properstop clearance before leg 13 is soldered into place. Note here that thesimple round terminal posts shown are a simplification. In practice theposts would preferably have at least some serrations to grip the plasticand ideally would be stamped from a piece having a larger cross-sectionand serrations in the plastic pockets so that they would not heat anddeform the plastic too much during soldering. The stamped parts couldalso facilitate positioning of the coil winding wire terminations duringthe winding and soldering process. It is particularly important that thepositioning attachment of the stop leg at 13 be stable.

General Optical Structure Description

In use there are six general rotor positions or positional ranges foreach revolution for which light readings may be taken. Depending on themode of operation, not every reading needs to be taken on everyrevolution and often the unit will operate in modes where only one or asmall number of the five revolutions will be used. Also, many of thereadings will be taken when the rotor is in motion so that readingpositions do not need to exactly correspond to the step positions. Thestep positions should, however, be positioned symmetrically with respectto the two color filter positions so that both position and rotationalvelocity can be duplicated as well as possible for correspondingmeasurements of the same viewing frame for each of the two colors.Furthermore, other designs or emphasis may require a different number ofcolor selections, three for example. Placement of too many mirrorsaround the head does raise problems with signal cross talk and requiresadded care in separation of the signals. Many inventive features arealso still present in a design which uses only one reflector which isoptionally uncolored without the use of the color selection. Also thetwo color design can use one substantially clear reflector and subtractthe color filtered signal from the substantially non color filtered oneto get the complementary component or use a processing algorithm whichdoes not use the directly complementary color component. Modificationsof the types described are considered to be within the scope of theinvention. In practice the head is panned back and forth only throughthe rotational range which includes the positions at which readings aretaken. Many readings can be taken for travel in each direction so thistransit time is not lost by taking readings for only one direction andthen doing nothing during the return in the reverse direction. Whilepanning through the headlamp dimmer's angular sensing range, theinterval between readings for successive frames of a given color may berelatively small, even in the millisecond range. The rate of panning mayvary substantially with mode of use but, very roughly, a set of readingsfor one back and forth cycle will be repeated in a range of once everyseveral seconds to several times a second. The rate may be adjusted evenduring a particular cycle depending on conditions. For example, theportion of the scan used to detect the most distant tail lamps may beslowed. Slower panning may permit more settling time and permitadditional readings to be taken and averaged to at least in part offsetlimitations in sensor noise and response speed for very low signallevels. It is a fortunate coincidence that the response speed normallyrequired for the above type of measurement tends to be correspondinglylow. The typical situation where the greatest sensitivity is required isin overtaking a vehicle which is a substantial distance ahead in acircumstance with dark surroundings. These are the circumstances underwhich the driver in the leading vehicle will be most bothered byheadlamp glare from the rear and for which the most distant and,therefore the dimmest lights, must be sensed. Things generally happenmuch faster for oncoming headlamps, and fortunately, the available lightlevels are also greater permitting faster response. The aboveconsiderations make it prudent to utilize some loss in contrast in thelens 2 to advantage. First, the loss in contrast is normally due tolight from a bright image being scattered over into another dimmerviewing area by reflections or light scattering from optical surfaces ofthe lenses, mirrors, filters, or portions of the case into which thelight is projected. With the measuring system the effect is to have veryhigh sensitivity in the area which is directly projected onto the sensorbut to also respond more weakly to scattered light from strong signalsnot directly in the field of view. The constructive use of a prudentamount of scattering will allow sensing of scattered light from brightoncoming headlamps which rather suddenly come into view before the unithas had time in its current scanning mode to pan to the place needed todirectly view the bright oncoming headlamp source. In such situations,the unit may respond by dimming the controlled headlamps immediately ormay verify the increased light readings by terminating the relativelyslow search for weak tail lamps to perform a more rapid scan for thesource of the increased background light level so that when it isrequired the appropriate dimming may take place without undue delay. Itshould be understood that the scattered light in the unit must be heldto a reasonably low level and the forgoing discussion is not intended tocontradict prior suggestions such as the one to use baffles to reducethe scattered or stray light. The point is that the difference inreceived light level between dim, distant tail lamps and modestly closeoncoming headlamps is huge and in this instance, the reading from even amodest amount of scattered light in the unit will be enough to achievethe stated objective. The control sequence is arranged so that duringoperation the mirrors are not allowed to dwell in a position range closeto that shown in FIG. 3 or the corresponding position range 180 degreesaway when the mirror 4b is aligned to reflect light which is focused bythe lens 2. As a result there is no chance to focus the sun's directrays on the sensor for a prolonged period of time thereby risking damageto the sensor. In fact the rotor is allowed to come to rest only in aposition where light coming through the lens is substantially blocked byone of the baffles 4c. This blockage occurs well before the light raysreach their focal point so there is no danger of seriously overheatingother surfaces either. The rotor is also moved to a position where thebaffles 4c block light from the lens 2 before the circuit de-energizesitself after the ignition is turned off. This prevents risk of damagedue to focusing the sun's rays when the unit is turned off and thevehicle is idle.

With these general understandings, the use of the rotational positionsand the translation feature will be described in more detail. For thefirst half, 180 degrees of rotation, of one revolution of the assembly,there are three positions approximately 60 degrees apart which yieldreadings for one of the two color filter selections. For the remaining180 degrees of the revolution there are three similarly spacedcorresponding positions for the other color filter selection. There arealso up to 5 revolutions which generally repeat the 6 positions perrevolution but for which the elevational viewing angle of the lightsensitive area for the headlamp dimmer increases by about one and onehalf degrees for each revolution of the assembly toward its lower stop.Note that the 31/4 degree frame size stays nearly constant but theelevational position of the whole frame changes. Focus is affected bythe translation of the rotor assembly and the unit is designed for bestfocus when the unit is approximately in the middle of the translationalrange so that focus is still acceptable at both extremes of thetranslational range.

FIGS. 3, 4, and 5 show the sensing head in viewing positions from thefirst half revolution for taking readings for the headlamp dimmer, forthe headlamp on/off sky sensor, and for the blocked light condition,respectively, with the red reflecting filter mirror 4a in theoperational position. There is a second red complement or cyanreflecting filter mirror 4b which assumes three additional positionsduring the second half revolution. Portions of both of the filtermirrors 4a and 4b are visible from the perspective shown in FIG. 4. Thegeneral operation is identical for measurements taken with 4b in placeof 4a and the appearance of the FIGS. 3, 4 and 5 is nearly identical tothe appearance when readings are taken with 4a except that 4a and 4b areinterchanged and the tab 4d is not visible. Thus figures are notincluded to show the positions for readings taken with the filter 4b.The mirror 4b is not placed in an exactly symmetrical position to 4a butis offset just enough to compensate for the 0.5 millimeter of axialmovement caused by the half turn of travel between the correspondingmeasurement positions for the two filters. In this way the field of viewfor each reading with the 4b filter more closely registers with thecorresponding field of view for the corresponding measurement taken onehalf revolution away with the 4a filter. That offset has beenestablished so that when readings are taken with the filter 4a, thecorresponding readings with 4b are taken with a rotational increment ofprecisely 180 degrees in a direction to advance the rotor away from homestop 4e. Note that the mirror 4b could have been offset the other way tocompensate for the half revolution of travel. Then the correspondingfields of view for 4b would be for a 180 degree increment of rotation ina direction advancing the rotor toward rather than away from the homestop 4e. The choice constitutes a sort of date line for the rotation andshould be chosen to correlate with the end stop position to avoid havingportions of the rotation next to the end stop for which it is notpossible to rotate to the corresponding frame of the other colorselection and stay within the end stop limits. This is an importantpoint because color determinations are made by comparing the readingstaken with the filter 4a with those of corresponding location taken withthe filter 4b. The more nearly the viewing frames for the correspondingcolor frames register, the more accurate the readings will be.

Headlamp Dimmer Specialized Sensing Function

Referring to FIG. 3, the rotary head 4 is in the position to read lightlevels for the headlamp dimmer. Ray 301 is a representative ray from thefront and may for example emanate from the headlamps of an oncomingautomobile, from the tail lamps of a leading vehicle, or may be a lightray reflected back from the automobile's own headlamps. The ray passesthrough the lens 2 and is focused as ray 302 which continues to themirror 4a which consists of a red transmitting filter with a reflectiveback. The combination reflector and filter 4a is constructed by applyinga reflective surface on the second surface side of either a glass or aplastic red transmissive filter. The filter is then secured in therotary head 4 in the position shown. The filter 4b is fabricated andsecured in a similar fashion. Incoming ray 302 then makes two passesthrough the filter material, one on its way to and a second on its wayfrom the second surface reflecting surface. The red component of the ray302 is reflected and continues as ray 303 which strikes the lightsensitive area 1a of the sensor 1. The lens 2 has a focal length ofabout 40 millimeters and is focused on the silicon sensing area 1a ofthe sensor 1 when the rotor is in its nominal center position. Thesensor 1 has an active area 1a about 0.090 inches on a side giving thedevice an instantaneous field of view which spans about three and onequarter degrees in both the horizontal and the vertical directions whenused with the 40 millimeter focal length lens. Note that the function ofthe lens is to bring substantially all of the rays emanating from agiven viewing area in the field of view to focus in a corresponding areaon the focal plane at the sensor surface. Thus the amount of lightcollected from a particular light and projected onto the sensor isdirectly dependent on the light receiving area of the lens 2. Whenever alight source in the field of view is small enough to project as oneimage on the active area of the sensor, the light level read from thisimage will include the reading of the color component from essentiallyall of the rays from the object which fall on the lens. An infraredrejecting filter is optionally included as part of the sensor 1. It maybe added just in front of the light sensitive aperture of the purchasedsensor, purchased as part of the sensor, or the sensor may be of a typewhich is not sensitive to infrared. As an option, the infrared filteringcan be included as part of the mirrors 4a and 4b. Rejection of theinfrared is not absolutely necessary but greatly enhances the ability todistinguish color. As a negative, much of the energy detected by asilicon sensor is in the infrared part of the spectrum so the alreadysmall sensor signals are even much smaller. These factors must bebalanced in the choice to reject the infrared wavelength component andin the choice of filter pass bands for the optical visible range lightalso. The first surface reflection of about 4 percent off of the frontsurface of the combined filter and mirror 4a is not color filtered. Inmost cases this should be permissible. Options to avoid or minimize thisunfiltered component are to use an anti-reflective coating on the faceof the mirror 4a, to use a red selective first surface reflector insteadof the second surface reflector, or to replace the reflecting filter 4awith a non-colored first or second surface reflector and to mount afilter which generally conforms to the outer cylindrical shape of therotor head 4 so that it spans the opening between the two baffles 4c andso that light rays entering from the lens 2 or the light pipe 3 passthrough it once on their way to the mirror 4a. A similar cyan filter isthen provided for the mirror 4b. The sensor is preferably an integratedphoto-diode and amplifier combination such as an automotive temperaturerange version of the Burr-Brown OPT201 combined photo-diode andamplifier supplied by Burr-Brown Corporation of Tucson, Ariz.

The viewing area is panned about 10 degrees to each side of the centerviewing position which is shown as the head 4 is rotated by about 25degrees to each side of the position shown. Thus, successive readings ofthe output of the sensor 1 are taken as the sensor head 4 rotatesthrough an angular excursion of about 50 degrees beginning about 25degrees before the position shown is reached and extending about 25degrees after the position is passed. The path of the scanned viewingarea remains reasonably close to the horizontal and the sensitivityfalls off some toward each extreme of the 50 degree rotational rangebecause the baffles 4c begin to interrupt the light coming from the lens2. The moving baffles 4c serve to substantially block light which entersfrom the light guide 3 during the scanning operation just describedwhere light entering through the lens 2 is being measured. Likewise thebaffles 4c serve to block light entering the lens 2 when the rotor head4 is in position to read the light from the light guide 3 and to blocklight from both sources when the rotor head 4 is in the position toblock light from both sources. It should be understood that forsimplicity only the more complex rotary baffle is shown. In practice anumber of additional stationary baffles should be added, for example,one directly around the light sensing aperture 1a of the sensor 1 wouldhelp considerably to reduce stray light readings. The general rule forplacement of the baffles is to avoid interfering with mechanical motionand with the primary optical paths but otherwise use baffles whereverthey are helpful enough to be economically prudent to add. Scatteredlight sources coming in at divergent angles and hitting the lens 2 canbe particularly troubling. Some external shading of the lens 2 byprojections from the case 100 in combination with added inside bafflesis prudent and anti reflective coating of the lens would be helpful ifneeded enough to be economically justifiable.

Similar successive readings which form matching pairs with correspondingreadings taken with the red filter 4a are taken for the cyan filter 4bwhen the rotor head 4 rotates through a range of angles displaced by 180degrees from the range just covered. The above description appliesgenerally except that the word red is replaced with cyan which hererefers to a filter which rejects red and transmits or reflects visiblecolors which are complementary to red.

At night when the headlamps are in operation, the desired elevationalangle for the headlamp dimmer sensor will be established by selectingthe number of turns to revolve the head 4 from its home stop positionand the amount of vertical panning used will be determined by the numberof revolutions over which light level readings are taken. Theelevational viewing angle changes by about one and one half degrees witheach revolution of the head. Thus, there is approximately 50 percentoverlap in the viewing frames from one revolution to the next. Betweenthe horizontal panning capability and the five vertically spaced scanlines it is possible to completely cover a viewing field which is about9 degrees high by about 20 degrees wide. In what follows, the nominalthree and one quarter degree approximately square viewing field or framewhich is projected onto the sensor's active area and for which a readingis taken will be referred to as a reading frame. Using this terminology,the approximate 50 percent overlap in viewing frames from one revolutionto the next, means that there is a corresponding 50 percent overlap intwo reading frames when the second reading frame is taken when the head4 has revolved exactly one revolution from the position where the firstreading frame was taken. The overlap in the horizontal direction can beadjusted to any desired amount by changing the rotational increment ofthe position of the rotor head 4 for which readings of the light levelare taken. A small rotational increment of the head 4 between readingframes results in many reading frames with large overlap and too large arotational increment results in viewing gaps between the reading frames.Each reading frame is taken with a field of view which is only about 6percent of the total field of view. Thus, for example, for a large areadiffuse light sources from the automobiles own headlamps which isreflected back from snow covered ground, the reading with the small areasensor may be less than a tenth of the reading averaged over the wholearea. On the other hand, the tail lamps of an automobile several hundredfeet ahead should all be visible in one of the 31/4 degree by 31/4degree frames and the reading for this frame should be substantially thesame as a reading of the tail lamp light level taken over the entire 9degree by 20 degree frame. This is true because essentially all of thelight from the tail lamps is projected into the one frame. Here theoverlapping frames enhance the ability to capture a reading for theframe where the lens 2 projects light from all of the tail lamps ontothe single sensor reading frame. This makes it possible to detect thetail lamps with greater sensitivity and uniformity than if their lightis split between adjacent non overlapping frames or worse yet lost ingaps between frames. The result of doing the overlapped scanning then isto raise the ability to distinguish the headlamps from a diffusebackground light level by about ten to one on the basis of intensityalone. When the capability to check that the lights are red is added,this advantage is even greater. The micro controller is programmed torespond to the lowest light levels only when they are from red lights.This screens out many low intensity, non-red light sources which wouldotherwise be confused with dim tail lamps and cause nuisance dimmingwhen operating at the very high sensitivities required to respond to thered tail lamps in time.

Headlamp On/Off Specialized Sensing Function

Referring to FIG. 4, the lens 2 is not actually removed from theassembly during operation but for visual clarity has not been shown inFIG. 4 to permit an unobstructed view of the light guide 3. The rotaryhead 4 has been rotated 60 degrees from the position shown in FIG. 3 andis in position to sense the red light component of the skylight. In thisposition the large area, cylindrical, negative focal length lens 3b ofthe light guide 3 directs some representative rays into the light guidefrom a large viewing area of the sky. Note that the cylindrical entrancelens was convenient here because of the geometry but other lensgeometries including more conventional spherical or aspherical ones areadvantageous in other applications and within the scope of theinvention. The light guide has a reflector applied to the surface 3f toreflect rays so that a reasonable percentage are directed along thelength of the light guide and are internally reflected off of the slopedend surface 3a. Some of these rays then continue through the light guidesidewall 3d where they project a diffuse area of light on the redreflector 4a which reflects a diffuse pattern of red filtered lighttoward the aperture 1a of sensor 1. Thus, the red content of theskylight is measured. A fairly low percentage of the light actuallyreaches the active area 1a of the photo-sensor but this is acceptablebecause of the relatively high threshold light levels for the headlampon/off function when compared to the dimmer function. When the rotaryhead 4 is indexed 180 degrees, operation is similar except that the cyanfilter 4b reflects the shorter wavelength non-red light to the sensor.

In normal operation, the micro computer takes the ratio of this cyanband pass filtered (4b) reading of the shorter wavelength visible raysto the red filtered band pass (4a) reading of the longer wavelengthvisible rays. On a blue sky day, the balance in spectral content isshifted toward the blue end of the visible spectrum and the ratiodetermined above is substantially higher than on an overcast day. Thecyan reading is better than the red reading as the basis for thethreshold level to be used to determine when to turn the headlamps on oroff. However, the use of a common threshold for both cloudy and cleardays even when using a single broadly filtered color component which isbetter than another color component still has not proven adequate toproperly establish the sensitivity for both the clear day and the cloudyday. The color balance measurement which depends on the taking of two ormore readings is required. When the ratio determined above is highindicating a blue sky day, a lower light level threshold is used todetermine when to turn the lights on or off.

Many variations of the above procedure are possible. In someconfigurations, the two or more readings required to determine the colorbalance may be combined implicitly in the sensor perhaps beforeamplification and effectively the color balance indication may bepreprocessed so that only one signal which is directly indicative of thecolor balance is input to the controller. It should also be understoodthat more than two color component measurements may be used to determinethe spectral color balance and that more than one signal can be used todetermine the general skylight level and that these two determinationsmay or may not be interdependent. Narrower parts of the spectrum mayshift in directions which may even be opposite to the general shifttoward the shorter wavelength distribution on a clear day. This isparticularly true when spectral absorption is changed due to compoundsin the atmosphere. The most notable example is that moisture absorbscertain rather broad bands in the infrared. This is the main reason forsome emphasis on the use of visible light in the preferred embodiment.Enough moisture is present to cause substantial attenuation in theinfrared absorption bands even on some days which are relatively cloudfree. Thus, the infrared absorption in itself is not considered to be agood indicator of skylight related driving conditions. However,practically any overcast day will show reduced solar radiation in thebands corresponding to the infrared absorption peaks of moisture. Thus,if the infrared component for wavelengths which correspond to theseabsorption bands are to be used in the determination of the spectralbalance, they should preferably be grouped with the blue visible lightand balanced against an overall spectrum or a spectrum in between theblue and the infrared. This is because the general tendency is forrelative radiation intensity to be diminished in both the infraredmoisture absorption bands and the short wavelength visible bands oncloudy days. A system which lumps infrared with short wavelength lightmay still work in accord with the principles of his invention but it isnot preferred.

An alternate statement for the control operating characteristic for thecase where the color balance is determined on the basis of at least twoseparate readings is as follows: The headlamp on/off controller appliesa given functional relationship to at least two skylight readings takenby applying different color filters or color responses to the skylightreadings to determine the relative spectral distribution of theskylight. An indication of a distribution which is strong in shorterwavelengths is indicative of a clearer, blue sky day. A skylight readingor combination of readings is also used to determine the indicatedskylight level. The functional response of the controller ischaracterized in that the operating headlamp turn on and/or turn offthreshold is at least in part based on the indicated skylight level andalso on the relative skylight spectral distribution. The operatingthreshold based on the indicated skylight level will generally be madelower when a spectral distribution indicative of clear, blue skyconditions is indicated by the given functional relationship. Thespectral distribution indicative of clear sky is one which has a greateramount of shorter wavelength light in the distribution. Certain parts ofthe infrared part of the spectrum which are absorbed by moisture arepreferably rejected or grouped with the short wavelength visible readingbecause a decrease in their intensity relative to the rest of thespectrum is also indicative of conditions which tend to be overcast.

In another case where a signal directly indicative of the color balanceis used, the control operating characteristic is as follows: Thecontroller utilizes two or more signals, a first given signal indicativeof the shorter to the longer wavelength color balance of the skylightand a second given signal or combination of signals indicative of theskylight intensity. The controller establishes an operating thresholdfor the headlamp on to off operation and/or the headlamp off to onoperation which is at least in part related to the two given signals orsignal combinations. The functional relationship between the signals issuch that for a higher short wavelength to long wavelength color balancegenerally indicative of a clear day, the operational light levelthreshold based on the indicated skylight level will be adjusted basedon the indicated color balance. The nature of the adjustment will be togenerally decrease the operating headlamp on to off or off to onthreshold as the short wavelength to long wavelength color distributionincreases.

In practice, in order to limit unwanted frequent switching of the lightsbetween on and off, various filtering and/or time delaying options maybe used in addition to the threshold determination referred to above andhysteresis may be added to modify the turn on threshold relative to theturn off threshold. It is intended that the base threshold be measuredin a common sense way and not in a way which would use time averaging,delaying or hysteresis effects to mask the effective operating thresholdof the control.

A copending application, assigned to the assignee of the presentinvention, Ser. No. 08/110,373, filed Aug. 23, 1993, and incorporatedherein in its entirety by reference contains related details on thelight pipe structure. The concave entrance lens 3b of the light guide 3is directed to receive light from the sky through the windshield of thevehicle. A feature which needs to be emphasized over the emphasis givenin the copending application, Ser. No. 08/110,373, is that, withappropriate design, the larger entrance lens area relative to thegeneral cross section area of the light guide enhances the pickuppattern and allows a greater light intensity to be directed into thelight pipe or light guide. In support of this point, with the concaveentrance lens design the sloped side 3c extends beyond the general crosssectional outline of the rectangular light guide cross section. The ray403 striking this side of the entrance lens from a divergent angle asillustrated is refracted to a direction more nearly parallel with theperpendicular center axis of the light guide entrance lens so that it iscaptured. Likewise the ray 404 entering from a divergent angle from theopposite side as illustrated is also refracted toward the center axis ofthe light guide so that it can enter the light guide. Neither ray wouldbe likely to have been directed into the light guide at an angle forwhich it would be transmitted were it not for the concave entrance lensand the edges of the lens which extend beyond the cross-sectionaloutline of the integrally attached light guide. The rays 401 and 402 areincluded to illustrate the general path followed through the light guideand in particular to illustrate how the light guide captures raysentering at divergent angles from the front and back. To achieve thedesired wide angle viewing area, light is not efficiently focused fromthe very small viewing field as it is by the lens 2. Instead, arelatively small but representative sample of rays entering over theintended wide angle viewing field must be captured and directed to theexit end of the light guide 3. In this process many other rays are lost.The entrance lens arrangement is generally designed so that rays fromthe right side of the viewing area are most likely to be captured ifthey enter the right side of the lens and so on. Design of the entrancelens to conform generally to this mapping criteria between the area onthe lens face where the light from a given part of the viewing fieldenters the lens and the relative efficiency of the system in directingthis light into the light guide helps to find a design such as the oneillustrated where the larger entrance area and the concave cylindricallens face are used to capture light from a wide angle input aperture anddirect more of it into the light guide. The ray 401 entering the frontportion of the viewing area is only mildly refracted and continues asthe ray 401a to where it is reflected off of the mirrored surface 3d andcontinues as the ray 401b. The ray 401b is internally reflected off ofthe angled end 3a and exits the light guide through the opposite side 3fas the ray 401c. The red component of the ray 401c is reflected off ofthe mirror 4a as the red component 401d which continues to the aperture1a of the sensor 1. A similar type of path is illustrated for the ray402 entering from the back portion of the viewing area. The descriptionof the path parallels that of the ray 401 and will not be repeated. Thetranslational motion caused by the successive revolutions of the rotorhead 4 are designed for the headlamp dimming function and have littleuseful effect for the headlamp on/off function. For consistency it isadvisable to choose a particular rotary position to use for the skylightreadings.

Blocked Light Sensing Function

In FIG. 5 the rotary head 4 has been turned 60 degrees in the otherdirection to the position where the light from the light guide 3 and thelens 2 are both blocked. This is the position where the dark referencereading is taken for the red reflector 4a. Since the stray light isdifferent with the red reflector 4a and the cyan reflector 4b, separatedark reference readings are taken at this 4a position and thecorresponding position for 4b 180 degrees away. The contribution ofstray light to the reference reading also depends somewhat on thetranslational position so it is prudent to also maintain a separateblocked light reading for any of the five rotary passes which are in useas well as for each color filter. This makes a possible requirement forten different blocked light readings. If the design is such that thestray light contribution is sufficiently low and relatively unaffectedby the filter and/or the revolution, some or all of these redundantreadings can be eliminated. It is advisable to perform some averagingand some integrity checks on the blocked light reference readings.Readings that are unexpectedly high should trigger re-initialization andre-homing of the device to restore proper operation in case that theactual rotary step position is different from the one indicated in themicro controller record.

Electrical Control Circuit

FIG. 7 is a block diagram of the micro controller based control circuitwith more detail given for the electronic drive circuit for the motor.The micro controller power supply receives power from both thecontinuous and the ignition switched automotive power supplies. Thesesignals as well as the various signals connected to the controlinterface 702 may be connected directly to the automobile's wiring ormay be routed through other modules such as a rearview mirror package.The power supply module 700 supplies a +12V signal to the seriesconnected stepping motor windings M1 through M5, and supplies +5V to themicro controller 701 and various required voltages to the sensor for itsintegrated amplifier and to the light sensor interface module. The powersupply 700 energizes the above circuits whenever the vehicle ignition ison supplying power on the ignition switched +12V input. The power supply700 also receives a controlling signal from the micro controller. Thepower supply 700 continues to supply power from the continuous +12Vsupply to the micro controller and the stepping motor and interfacemodules after the Ignition Switched +12V is turned off. The microcontroller keeps the headlamps on for an exit delay period as requiredand indexes the motor rotor 4 to a position where the partition wall 4cof the rotor (See FIG. 2) blocks light entering from the lens 2 beforeit reaches a focus point so that the lens will not cause damage to thesensor or other components should the vehicle happen to be parked wherethe sun is in the viewing field of the lens 2. After the tasks arecomplete, the micro controller sends a signal to the power supply toturn off the supplies including the +12V to the motor and the +5V supplyto the micro itself. In some applications, such as for testing or fortaking a measurement for the vehicle solar load, it may be necessary to"wake up" the circuit to take measurements or perform some otherfunction. The circuit ground connection GND connects to the automotiveground. The headlamp dimmer and the headlamp on/off control interfaceincludes options to enable or disable the automatic functions along withoptional sensitivity and exit delay functions and indicator lights.These functions can be incorporated on a small panel next to the mirrorsurface of the automobile's rearview mirror or optionally at some otherconvenient location. The control interface 702 sends and possiblyreceives signals particularly if the control communicates with othercontrol modules over a communication bus. Signals are sent to turn thevehicle headlamps, tail lamps, and running lamps on and off as required.This automatic command is paralleled by the manual switch which thedriver can use to override the headlamp on/off control at any time.Another output controls the high beams and outputs are also availablefor other modules in the vehicle such as the ambient light signal for arearview mirror. Other signals used to calculate heat load for theclimate control, or to control the intensity of instrument panellighting are also available. The motor windings M1 through M5 are thewindings placed on poles P1 through P5 in FIG. 6. It should beunderstood that the system can be adapted to work with the pole windingsconnected in nearly any order if the switching order is appropriatelyadjusted and if each of the poles are energized to the required polarityby the circuit. For the configuration shown each pole must be energizedto the same polarity by the series current from the +12V terminal to theGND terminal. Since description of the switching sequence is easier ifeach pole in order is connected in series with its neighbor, this is thearrangement assumed for the description which follows. Transistors Q1through Q5, respectively, short individual windings M1 through M5.Whenever a particular transistor which has been turned on is turned off,the current will be maintained by the inductances of the non shortedwindings which are in series. A large voltage spike would occur if itwere not for the parallel resistors R1 through R5. The resistors do noteliminate the spike but are sized to limit its peak voltage to anacceptable value. Capacitors or resistor--capacitor networks may be usedin place of R1 to R5. Q5 is turned on directly to short winding M5 whenoutput S5 of the micro controller is driven high supplying base currentthrough R14 to Q5 thereby turning on Q5 and diverting current from M5 sothat it is no longer driven to its active state. The effective shortwhich is created across M5 does not cause the current in M5 to decayimmediately. Instead it decays with an L/R time constant where L and Rare the inductance and resistance, respectively, of the shorted winding.Driving output S5 low turns off Q5 and allows the series winding currentto energize M5. Shorting of the Q4 is similar except that Q9 isnecessary to shift level from the ground based micro controller outputS4 to the base of the shorting transistor Q4. Driving S4 high suppliesbase current through R13 to Q9 which turns on drawing current throughcurrent limiting resistor R9 from the base of the pnp shortingtransistor Q4 turning it on and shorting the winding M4. When S4 isdriven low, Q9 and Q4 both turn off and R18 maintains a near zerovoltage at the base of Q4 to assure its complete turn off. The action ofthe winding inductance and the L/R decay are similar to that alreadydescribed for M5. The Shorting of M1, M2, and M3 is similar. Resistor R6is normally made higher resistance than R7, and R7 higher resistancethen R8, and R8 higher resistance than R9, the resistance values beingsized to cause the flow of adequate but not excessive current to turn onthe respective transistors Q1 through Q4.

Adequate steps must be taken to prevent the turn on of all of thetransistors at one time or to short circuit current limit the +12Vsupply to M1 in such a way that damage will not be done if the shortingtransistors are all turned on together by a malfunction of thecontroller. One way to provide reasonable assurance that the windingswill not all be shorted at the same time is to provide for the inverteddrive of S1 indicated by S1'. In this way, a fault condition in whichall of the outputs S1', S2, S3, S4, and S5 are driven highsimultaneously will not short Q1. It is much less likely to have S2, S3,and S4, S5 inadvertently driven low and to have S1' simultaneouslydriven high. In operation the circuit of FIG. 7A replaces R10, Q6, R6,R15, and Q1. and the micro controller is programmed to supply aninverted signal S1' in place of the signal S1. When S1' is pulled low,current is drawn from the emitter of Q6A through current limitingresistor R10A. The base current of Q6A remains small and current fromthe emitter of Q6A is drawn mainly through the collector of Q6A and thusfrom the base of Q1A turning it on and shorting winding M1. When theoutput S1' is driven high by the micro controller, the currents are nolonger drawn and the shorting transistor Q1A turns off.

The sensor interface 704 conditions the signal from the light sensor 1so that digital readings of the sensor output may be read by the microcontroller as required. The light sensor 1 is the one depicted also inFIGS. 2, 3, 4, and 5.

Motor Stepping Sequence

FIG. 8 indicates a complete 10 step stepping sequence for the motor. Theentry for each step has three sections, first a sequence number which issimply to refer to the step and to keep the steps in their proper cyclicorder. It makes little difference which step is listed first, but eachstep has a definite successor in the cyclic order. The five columns S1through S5 give the micro controller output drive state for thetransistor pole shorting circuit. An "H" indicates that the microcontroller outputs a positive voltage to turn on the shorting circuitfor the corresponding pole. An "L" indicates that the micro controlleroutputs a low signal to turn off the shorting circuit for the particularpole so that the winding around it is energized to drive it to itspredetermined state. The list with the five columns P1 through P5 liststhe polarity to which a pole is driven by the winding which encirclesit. An "N" indicates active drive of the winding encircling theindicated pole face to its north pole state. Rather arbitrarily, thenorth pole magnetic polarity is used for the actively driven poles. A"-" indicates that the pole is not driven by its encircling winding.

There are 10 distinct entries in the list which are identified by indexnumbers 0 through 9. The first repeated step with index 0 is alsoincluded at the bottom of the list. The stepping sequence for rotationin a given positive direction is to start at the present state and tothen go to the next state as indicated by the state for the next higherindex number until the present state is that shown for index 9 in whichcase the next state is shown by index 0. For steps in the reversedirection the stepping sequence is the same except the direction in thetable is from the present state to the state indicated by the next lowerindex number until the present state is that shown for index 0 in whichcase the next state is shown by index 9.

Because the sequence has only ten distinct drive configurations, therotor can be forced to "jump" to a position some integral multiple often steps away which has the same magnetic drive state. For example, therotor if mechanically forced from its step position will when releasedjump to the nearest position which corresponds to the one of the 10magnetic states to which the motor is being driven. This may not be theposition from which it was mechanically forced. As another example, ifthe step position is jumped by 5 steps the motor will not know whetherto move five steps ahead or five steps back. If the step position isindexed by two, three, or four steps at a time, the motor will index tothe proper position provided that stepping conditions are ideal. Themore steps taken at one time, the less margin there is for additionalmotor displacements caused by load forces, settling times of motorwinding currents, or forces due to the rotor or rotor load acceleration.For indexing two steps at a time, there is still reasonable margin toprevent losing step and going to the wrong position.

FIGS. 8 and 9 illustrate that for each of the even numbered steps, threewindings are simultaneously energized driving their poles to the northpole polarity with the remaining two poles being shorted. For each ofthe odd numbered steps, only two of the pole windings are energized, theother three pole windings being shorted. As previously indicated, it isdesirable to drive a majority of the poles and also to drive the samenumber of poles. It is reasonable to double step and use only the evennumbered step positions. FIG. 9 lists only the even numbered steps touse for this sequence. As indicated before, the micro controller canswitch between various stepping modes to use the one whose particularadvantages outweigh its disadvantages for a particular part of the stepsequence. It is highly advantageous to use the stepping sequence forwhich a majority of the poles are energized for many applications.However, with flexibility to change the drive step sequence, it remainsan option to use other stepping sequences as desirable.

Alternate Embodiment of Sensing Head

Referring to FIGS. 10, 10a, 11, and 11a, the unit shown in simplifiedform is an alternate embodiment of the sensing head 4 of FIG. 2. Thehead 4 of FIG. 2 has the advantage of compactness and simplicity andability to operate with a low cost stepping motor having very modestpositioning resolution. The head 200 of FIGS. 10 and 11 is best usedwith a stepping motor or other positioning device with precise angularpositioning capability. It has advantages in being capable ofmultiplexing between many more closely spaced signal sources, of beingmore adaptable to a larger number of filter selections, and of beingcapable of efficiently coupling the sensor to light pipes of relativelysmall diameter. It is also possible to perform a spatial scanningoperation with the alternate embodiment. The blocked light reading mayalso be taken and used to correct for residual reading errors. Thealternate embodiment depicted in FIG. 10 is of particular value in suchapplications as reading color where it is advantageous to couple to oneor more light pipes and where it is advantageous to select from aminimum of three filters and to use six or more without seriousdifficulty in various embodiments. The unit is also adaptable to samplelight directly transmitted to a port. This option is not illustrateddirectly but could be implemented by removing the lens and using thevacated position to allow light from an external source to directlyimpinge on the port in that position. Appropriate baffles should beadded to shield other inputs from the external light source.

In FIG. 10, the cylindrical member 200 is in the rotary position tosense light focused on the aperture 200a by the lens 207, filter it, andproject it onto the sensor. In addition to the lens 207, five lightpipes, serving as optical signal sources, are arranged around theperiphery of the rotary cylindrical member 200 so that the end of anyone can be aligned with any of the viewing ports 201a, 201b, or 201c toselectively filter and read the light level emanating from them. Thelight pipes 208 to 212 and the lens 207 must be correctly aligned andthe light pipe ends are preferably close to the cylindrical surface 200but not touching it so they do not abrade it or impede its rotation.With the close spacing, the ports 201a, 201b, and 201c can be close to acommon plane of focus with the light pipe ends and thereby serve as aprecise optical sampling frame limiting baffle for the head. With properfocus and alignment of the lenses 203a, 203b, and 203c, the alignedlight pipe end or the aligned portion of the image focused by the lens207 are focused onto the sensor's surface. With such an arrangement, theoptical sources may be more numerous and more closely spaced than shown.The sources are arranged so that the angle of the axis of the lens 203awill not deviate from the normal to the sensor by more than 35 degreesfor positions for which readings are taken. If fewer sources are used orif it is convenient to space them more closely, it is desirable tominimize the off axis angle between the sensor normal and the axis of alens when it is aligned to take a measurement.

FIG. 10a is a top view of the configuration of FIG. 10. FIG. 11 isanother view of the same device as FIG. 10 for which the rotary head 200has been rotated so that the optical signal from the end 209a of thelight pipe 209 is aligned with the port 201a, filtered by the red filter202a and focused on the aperture 204c by the lens 203a. FIG. 11a is atop view of the configuration shown in FIG. 11. The rotary head 200 isrotated to align the remaining four light pipes with the aperture 201ain similar fashion. Likewise, the apertures 201b and 201c having greenand blue filters, respectively, are rotated into position to read aninput signal from any of the six optical signal sources. There is stillample space to position the rotary head 200 so that no optical source isaligned with one of the optical ports 201a, 201b, or 201c and to take ablocked light reading to be used to compensate for residual readingerrors.

Referring to FIG. 10 and the related FIG. 10a, the cylindrical unit 200has a hub 206 which connects to the stepping motor shaft 205. The sensor204 is preferably a silicon photo-diode having leads 204a and 204b whichare connected to an appropriate high sensitivity current to voltageamplifier. If the sensor does not have an integral amplifier it ispreferably used with a signal conditioning means which measures itscurrent while maintaining nearly zero volts across it. The sensor or thecomposite sensor filter module 204 preferably incorporates any filteringsuch as infrared rejection filtering which is common to all of the lightinputs. Filtering needed for all measurements made on a particularsignal source can be placed in the optical path of the signal before itreaches an input port of the rotary head 200. The light sensitive windowis 204c and the sensor is preferably attached to a printed circuit boardand held precisely in its stationary viewing position. The lightsensitive area on the sensor must be capable of receiving light from offaxis angles large enough to provide for both the off axis rays in theoptical system and for the off axis alignment of the signal sourcereading configurations with the sensor window 204a. The sensing aperture204c on which light to be sensed is focused is centered on therotational axis of the rotary cylindrical unit 200. The lens 220 and thefive light pipes 208 through 212 are the six light signal inputs. Theseinput sources are normally fixed in stationary positions and are placedso that the aperture 200a is precisely aligned with the end of each ofthe respective light pipes when a light reading for it is taken. Thelenses 203a, 203b, and 203c and the filters 202a, 202b, and 202c are allrigidly attached to and rotate with the cylindrical member 200. Forclarity, light baffles have not been shown. In practice, each of thethree lens and port assemblies should normally be enclosed by a shroudso that the sensor aperture 204c would be fully shielded from straylight rays from parts of the structure not part of the intended opticalpath. Such shielding should also be provided at the ports when they arenot aligned with an input signal and around input signal sources so theydo not interfere one with another. With such shielding, the signals willnot interfere to an objectionable degree with one another and the rotaryhead can be positioned so that light to the viewing ports is adequatelyblocked to take a blocked light reading.

Only a short portion of each of the light pipes 208 to 212 close to thesensing head is shown. In the complete structure the light pipes aresecured mechanically and adequately baffled. In a configuration for aheadlamp dimmer, headlamp on/off, and ambient light control, one lightpipe is coupled to an entrance lens which has a concave entranceaperture of substantially larger diameter than the light pipe crosssection. The entrance aperture is directed toward the sky through thevehicle windshield to detect the skylight. Another light pipe with asimilarly designed wide angle aperture is directed through thewindshield toward the front of the vehicle to sense the ambient lightlevel. See the aforementioned copending application, Ser. No. 08/110,373for a discussion of design considerations for sensing heads to directlight into a light pipe from a particular viewing area from which lightis to be sampled. Another one or several of the light pipes may be usedto sense light rearwardly of the vehicle to detect glare for the purposeof determining when to dim the rearview mirror. The control may have torespond to very low rearward light levels to dim the mirror under someconditions. Since the viewing area is relatively restricted, a convexlens can be used to concentrate the light level which is directed intothe light pipe to relatively a modest degree. It must still be realizedthat in most applications where the sensor must cover even a modestlylarge viewing angle, the level of light introduced to and transmitted inthe light pipe cannot realistically be concentrated to a level which isvery many times greater than the level which is sensed. Thus, care mustbe taken to keep the light pipe diameter large enough to transmit enoughlight so that a practical measurement can be made by the photo-sensor.The lens 207 can be used for the headlamp dimmer application. Otherautomotive applications are to direct light from a rain sensor mountedon the windshield. The sensing head of FIGS. 10 and 11 has even greaterapplication in reading light levels for color sensing applications.Lenses or light pipes are two practical ways to couple optical signalsto the unit. The red, green, and blue filters and their associatedlenses and sensing ports are aligned in turn with a signal source andreadings of the color components are taken.

Some of the particular beneficial objectives which may be met singly orin combination are as follows: The blocked light level may be sensed forcompensation. Light emanating from a light pipe can be efficientlyfocused on the sensor. The same sensor can be used with a number ofdifferent filter selections. The same sensor with the optional filteringselections and the optional blocked light compensation may be used toread an input from any one of a number of light signal sources which canbe coupled to the unit in any of a number of ways including directly, bya lens, or by a light pipe. Furthermore, a number of sources may bemultiplexed to the unit so that one or more lenses, one or more directinputs and/or one or more light pipes may be coupled to the head at thesame time. Additionally, the light from the lens, the direct input orfrom certain light pipe arrays can be spatially scanned. Especially incolor sensing applications, the between reading balance gained by usingthe same sensor and amplifier for reading the various color componentsnot only saves on sensor cost but may substantially increase theaccuracy of the measurement by eliminating errors due to sensor separatereading errors of individual sensors.

The lens 203a is aligned to bring the opening 201a at the periphery ofthe rotary member 200 to focus on the stationary light sensitive area204c of the light sensor 204. Thus, the lens 203a serves to focus lightwhich is projected on the port opening onto the sensor face. If the lens203a is made of a high enough F number to capture the cone of lightwhich emanates from the light pipes 208 through 212, it can be veryefficient in projecting a substantial proportion of the light whichemanates from the light pipe which is aligned for sampling onto thesensor aperture 204c. Light from the aperture 201a first passes throughthe red filter 202a so that the red component of light from the aperture201a is projected onto the sensor. It is preferable to make the sensingaperture 204c large enough so that the entire projected image of theaperture 201a falls within the sensing aperture 204c for all of theangular positions for which readings are taken using this aperture.

In FIG. 10, the cylindrical member 200 is shown in the position to readthe light level of the portion of the image projected by the lens 207which falls on the measuring port aperture 201a. This sequence will bedescribed one step at a time. Lens 207 is positioned to focus the lightin its intended field of view onto the periphery of the rotarycylindrical member 200. Note that this periphery is the area throughwhich the viewing or sensing ports of the rotary head 200 move. Theportion of this projected image which falls on the aperture 201a passesthrough the filter 202a and is re-focused by the lens 203a onto thesensing aperture. The sensor 204 generates a signal which in anapplication is coupled to an amplifier or other signal conditioningdevice by electrical connections made to the leads 204a and 204b. Inmany instances an alternate configuration can be used where all or aportion of this signal conditioning device is integrated in the sensorpackage and in some cases can even be integrated on the same siliconchip as the sensor. The Burr-Brown device referenced previously, may beused. Changes may be made in the member 200 as required to physicallyaccommodate a particular sensor. The amplifier or signal conditioningdevice generates a signal indicative of the light level which is inputto a controller or to a readout device or to both in order to performthe function intended for the light sensor. In normal operations, acomputer, micro controller, or other device which will generally bereferred to as a controller is used to register the reading and to stepa motor (not shown) the shaft 205 of which rotates the head 200 to itsrequired positions. A stop or a position sensing device may be used sothat the controller can establish the position of the head 200 in orderto control motion of the head to its required position. One method ofestablishing position has already been detailed for the device of FIG.2. The required sequence of readings is taken and processed by thecontroller and the appropriate readouts are indicated or controlfunctions performed.

In FIG. 10, the cylindrical member 200 is positioned to receive anoptical signal from the portion of the image focused on the sensingaperture 201a by a stationary lens 207. As the head 200 is rotatedthrough a relatively small angle, new portions of the image projected bythe lens 207 fall on the aperture 201a, are filtered by the filter 202a,and are in turn projected on the sensor aperture 204a by the lens 203a.The lens 207 is made large enough so that for a limited travel of theaperture 201a in the projected field of the lens 207, rays from the lens207 still strike all of the surface of the lens 203a. The requirementhere (approximating the lenses as thin lenses) is that for any positionof the aperture 201a in the projected field of the lens 207 for which areading is taken, straight lines drawn from any point on the surface ofthe lens 203a through any point in the aperture 201a should intersectthe lens 207. If the diameter of the lens 207 is too small to meet thisobjective, the measured intensity will be reduced for positions forwhich the portions of the lens 203a are shadowed from the full view ofthe lens 207. As with the device of FIG. 2, an optional feature topermit relatively small linear displacement of the head 200 along theaxial direction of its shaft 205 may be used to adjust the position ofthe aperture 201a in a direction perpendicular to the direction of itsrotary motion to achieve a two dimensional scan of the image projectedby the lens 207. Alternately the lens or sensor may be moved or someother means used when it is necessary to include a scan in a directionother than that provided by rotation of the member 200. Whenever axialdisplacement of the member 200 is used, the proper displacement must berestored to align the sensing head with the light pipes or other lightsources.

The head is indexed 120 degrees counterclockwise (viewed from the top)to align the lens 203b and the green filter 202b through the aperture201b. Then the green color component is measured in a manner identicalto that used to measure the red color component. Then the head isindexed 120 degrees further to align the lens 203c and the blue filter202c to measure the blue component of the light through a similaraperture 201c. More, or fewer, lenses and filter units may be positionedradially around the unit as the selection of more or fewer separatefilter combinations is required. The filter color transmissioncharacteristics are chosen to fit the application and do not need to bethe red, green, and blue suggested.

An identification of and/or typical values for the components of thesystems which are described hereinabove are as follows:

    ______________________________________                                        R1          Resistor    68 ohm 0.5W                                           R2          Resistor    68 ohm 0.5W                                           R3          Resistor    68 ohm 0.5W                                           R4          Resistor    68 ohm 0.5W                                           R5          Resistor    68 ohm 0.5W                                           R6          Resistor    1.2K ohm                                              R7          Resistor    820 ohm                                               R8          Resistor    560 ohm                                               R9          Resistor    470 ohm                                               R10         Resistor    1.0K ohm                                              R10A        Resistor    1.0K ohm                                              R11         Resistor    1.0K ohm                                              R12         Resistor    1.0K ohm                                              R13         Resistor    1.0K ohm                                              R14         Resistor    470 ohm                                               R15         Resistor    10K ohm                                               R15A        Resistor    10K ohm                                               R16         Resistor    10K ohm                                               R17         Resistor    10K ohm                                               R18         Resistor    10K ohm                                               Q1          Transistor  Motorola MPS2907A                                     Q1A         Transistor  Motorola MPS2907A                                     Q2          Transistor  Motorola MPS2907A                                     Q3          Transistor  Motorola MP52907A                                     Q4          Transistor  Motorola MPS2907A                                     Q5          Transistor  Motorola MPS2222A                                     Q6          Transistor  2N3904                                                Q6A         Transistor  2N3904                                                Q7          Transistor  2N3904                                                Q8          Transistor  2N3904                                                Q9          Transistor  2N3904                                                ______________________________________                                    

It will be understood that these values, and/or descriptions may bevaried depending upon the particular application of the principles ofthe present invention.

SUMMARY

The focus of the foregoing has been to provide an improved sensingconfiguration for a combined headlamp dimmer and a headlamp on/offcontrol. Most of the features relevant to one or the other of thesefunctions in the combined control are equally applicable to thecorresponding function in a separate headlamp dimmer or headlamp on/offcontrol. It should be recognized that certain features have manyapplications beyond the narrow application to the headlamp control.First, the stepping motor is novel and should find application in manyareas quite independent of the headlamp control and independent of thetranslational feature.

Second, a number of the novel scanning, and color sensing features ofthe headlamp dimmer control can be performed by a multi-element siliconsensor or even by a video array. Of foremost importance is the abilityto partition the field of view into smaller areas so that as taughtpreviously, the diffuse light reflected from objects by the vehicle'sown headlamps or coming from other sources over the total field of viewdoes not drowned out the signal from the relatively weak tail lamps. Redcolor sensing to distinguish the tail lamps is also applicable and itsoptional but highly desirable use significantly improves the quality ofthe control function. Even the overlapping frame feature can beeffectively incorporated by providing a soft focus which spreads thelight from a point source such as a distant tail lamp over a half pixelor so. Depending on the specific arrangement, there is a great deal oflatitude in the amount of soft focus which may be either intentionallyintroduced or utilized as part of a lower cost lens system. The intentis to moderately spread light rays so that as the rays from an imagedlight source move from one pixel to another, part fall on an adjoiningpixel sooner, thereby softening the transition as the readout shiftsfrom one pixel to another. This creates a localized spatial averagingeffect on the signals generated. For the purposes of analyzing thesignal, this localized averaging effect on the response as the light inthe projected image moves from one pixel to another in the dynamicdriving situation can be of considerable advantage reducing the need toaccomplish a similar function by a computation intensive digital means.Another important advantage is that the enlarged image of the soft focusprevents the loss of signal which occurs if the image is sharply focusedon a non responsive boundary between pixels so that no pixel respondsproperly to the optical signal. Thus, the inherent averaging canactually reduce the complexity of the controller program which processesthe data in addition to allowing the use of lower cost optics. As withthe preferred device, the total field of view of the array sensor shouldbe generally limited to that for which headlamps from the vehicle withthe control are likely to cause glare for the driver of another vehicle.It is for this field of view that the headlamp dimmer control needs tosense the headlamps or tail lamps of other vehicles and respond byswitching the lights to low beam. Introducing an excessively large fieldof view increases the risk of damage from focused rays of the sun. Also,it either introduces unnecessary nuisance dimming because of response tolight sources which are in a field of view for which dimming is notrequired or necessitates extra control complexity to mask response tolights in these areas. It may also be generally wasteful of resources toprovide imaging capability where it is not required.

An array sensor, especially a black and white one, may have the samehigh response to infrared from tungsten light sources as do manyindividual photo-diodes. With the increasing use of red light emittingdiodes which emit little energy in the infrared range and more efficientgas discharge headlamps with greatly reduced infrared emission, it isprudent to assure that the sensor's infrared response is reasonablysmall and to eliminate at least a significant proportion of the sensorsinfrared response if it is not. The easiest way may be to use aninfrared rejecting filter. If the infrared is not rejected and if thesensor has the same high response to infrared that many siliconphoto-diodes have, eighty percent or more of the sensor's response tored tail lamps or even to headlamps may be due to the infrared. To adriver, it makes no difference whether the lights from another vehiclecontain the strong infrared component or not so the effect of notreducing the high infrared response is to cause a mismatch of the orderof five to one in the way that the control's sensor judges brightness ofvarious light sources versus how the drivers see them. The generalproblem of rejection infrared is certainly not new. Vactec, now EG&GVactec, has sold silicon photo-diodes with integrally incorporatedinfrared rejection filters since the late 1970's.

As indicated previously, the alternate embodiment of the rotary sensinghead has many advantages which make it useful for color sensinginstrumentation. These advantages include the ability to multiplex yetcouple efficiently with optical signal sources from light pipes, theability to select from a number of filter choices, the ability to useonly one sensor, the ability to block light from the signal sources totake a blocked light reading and use it for correction or partialcorrection of the sensor readings, the ability to also use the projectedimage from a lens as a signal source and to scan the image field of thelens, and the ability to use a direct input signal source. Additionallythe use of the common sensor and readout means minimizes the negativeeffect of a number of readout errors on color balance measurements.

While preferred embodiments of the invention have been illustrated anddescribed, it will be understood that various changes and modificationsmay be made without departing from the spirit of the invention.

What is claimed is:
 1. A control system automatically controlling theenergization and de-energization of electrically energizable headlampson an automotive vehicle, said control system comprising, incombination, means sensing the relative spectral intensities of theskylight levels of a broad area of the sky, said sensing means includingmeans taking at least two skylight readings with different colorresponses and measuring the balance between a color component which isweighted towards the short wavelength part of the color spectrumrelative to another differently weighted color component todifferentiate between a cloudy sky and a blue sky, and means in saidcontrol system effective to energize and de-energize said headlamps as afunction of the measured balance.
 2. A control system automaticallycontrolling modes of energization and de-energization and brightness ofelectrically energizable headlamps on an automotive vehicle, saidcontrol system comprising, in combination, sensing means taking at leasttwo skylight measurements with different color responses, said sensingmeans including means measuring the balance between a color componentwhich is weighted towards the short wavelength part of the colorspectrum relative to another differently weighted color component todifferentiate between a cloudy sky and a blue sky, and means in saidcontrol system controlling the modes of energization and de-energizationand brightness of said headlamps as a function of the measured balance.3. The combination as set forth in claim 2, said sensing means includingat least two color filters.
 4. The combination as set forth in claim 2,one of said sensor measurements being in the cyan range of the colorspectrum, another of said measurements being in the red range of thecolor spectrum.
 5. The combination as set forth in claim 3, said controlsystem utilizing the relationship between multiple measurements throughdifferently colored filters in making a determination to select thedesired brightness mode of said headlamps.
 6. A control systemautomatically controlling the energization and de-energization ofelectrically energizable headlamps on an automotive vehicle, saidcontrol system measuring the relative spectral intensities of the lightlevels of a broad area of the sky, said control system applying apredetermined functional relationship to at least two different colorresponses of said system to establish the relative spectral distributionin the light from the sky to determine whether the light is bluish inbalance indicative of a clear sky or less bluish in balance indicativeof an overcast sky, said control system operating in response to a lessbluish balance to adjust the light threshold at which the headlamps areenergized to favor energizing the headlamps during overcast conditions.7. The combination as set forth in claim 6, said system including atleast two color filters.
 8. The combination as set forth in claim 6, oneof said system measurements being in the cyan range of the colorspectrum, another of said system measurements being in the red range ofthe color spectrum.
 9. The combination as set forth in claim 7, saidcontrol system utilizing the relationship between multiple measurementsthrough differently colored filters in making a determination to turnsaid headlamps on or off.
 10. The combination as set forth in claim 6,said control system applying different color responses above and below620 nm to determine whether the light from the sky is clear or overcast.